diff --git a/dodam-api/src/main/java/b1nd/dodamapi/nightstudy/NightStudyController.java b/dodam-api/src/main/java/b1nd/dodamapi/nightstudy/NightStudyController.java
index 5ee240bb..a9ec8638 100644
--- a/dodam-api/src/main/java/b1nd/dodamapi/nightstudy/NightStudyController.java
+++ b/dodam-api/src/main/java/b1nd/dodamapi/nightstudy/NightStudyController.java
@@ -4,6 +4,7 @@
 import b1nd.dodamapi.common.response.ResponseData;
 import b1nd.dodamcore.nightstudy.application.NightStudyService;
 import b1nd.dodamcore.nightstudy.application.dto.req.ApplyNightStudyReq;
+import b1nd.dodamcore.nightstudy.application.dto.req.RejectNightStudyReq;
 import b1nd.dodamcore.nightstudy.domain.enums.NightStudyStatus;
 import b1nd.dodamcore.nightstudy.application.dto.res.NightStudyRes;
 import jakarta.validation.Valid;
@@ -35,21 +36,21 @@ public Response cancel(@PathVariable Long id) {
 
     @PatchMapping("/{id}/allow")
     public Response allow(@PathVariable Long id) {
-        nightStudyService.modifyStatus(id, NightStudyStatus.ALLOWED);
+        nightStudyService.modifyStatus(id, NightStudyStatus.ALLOWED, null);
 
         return Response.ok("심야자습 승인 성공");
     }
 
     @PatchMapping("/{id}/reject")
-    public Response reject(@PathVariable Long id) {
-        nightStudyService.modifyStatus(id, NightStudyStatus.REJECTED);
+    public Response reject(@PathVariable Long id, @RequestBody RejectNightStudyReq req) {
+        nightStudyService.modifyStatus(id, NightStudyStatus.REJECTED, req.rejectReason());
 
         return Response.ok("심야자습 거절 성공");
     }
 
     @PatchMapping("/{id}/revert")
     public Response revert(@PathVariable Long id) {
-        nightStudyService.modifyStatus(id, NightStudyStatus.PENDING);
+        nightStudyService.modifyStatus(id, NightStudyStatus.PENDING, null);
 
         return Response.ok("심야자습 대기 성공");
     }
diff --git a/dodam-api/src/main/java/b1nd/dodamapi/outgoing/OutGoingController.java b/dodam-api/src/main/java/b1nd/dodamapi/outgoing/OutGoingController.java
index d21e068a..13a6373f 100644
--- a/dodam-api/src/main/java/b1nd/dodamapi/outgoing/OutGoingController.java
+++ b/dodam-api/src/main/java/b1nd/dodamapi/outgoing/OutGoingController.java
@@ -2,6 +2,7 @@
 
 import b1nd.dodamapi.common.response.Response;
 import b1nd.dodamapi.common.response.ResponseData;
+import b1nd.dodamcore.outgoing.application.dto.req.RejectOutGoingReq;
 import b1nd.dodamcore.outgoing.application.dto.res.OutGoingRes;
 import b1nd.dodamcore.outgoing.domain.enums.OutGoingStatus;
 import b1nd.dodamcore.outgoing.application.OutGoingService;
@@ -29,21 +30,21 @@ public Response apply(@RequestBody @Valid ApplyOutGoingReq req) {
 
     @PatchMapping("/{id}/allow")
     public Response allow(@PathVariable Long id) {
-        outGoingService.modifyStatus(id, OutGoingStatus.ALLOWED);
+        outGoingService.modifyStatus(id, OutGoingStatus.ALLOWED, null);
 
         return Response.noContent("외출 승인 성공");
     }
 
     @PatchMapping("/{id}/reject")
-    public Response reject(@PathVariable Long id) {
-        outGoingService.modifyStatus(id, OutGoingStatus.REJECTED);
+    public Response reject(@PathVariable Long id, @RequestBody RejectOutGoingReq req) {
+        outGoingService.modifyStatus(id, OutGoingStatus.REJECTED, req.rejectReason());
 
         return Response.noContent("외출 거절 성공");
     }
 
     @PatchMapping("/{id}/revert")
     public Response revert(@PathVariable Long id) {
-        outGoingService.modifyStatus(id, OutGoingStatus.PENDING);
+        outGoingService.modifyStatus(id, OutGoingStatus.PENDING, null);
 
         return Response.noContent("외출 대기 성공");
     }
diff --git a/dodam-api/src/main/java/b1nd/dodamapi/outsleeping/OutSleepingController.java b/dodam-api/src/main/java/b1nd/dodamapi/outsleeping/OutSleepingController.java
index 6c316479..9e84e976 100644
--- a/dodam-api/src/main/java/b1nd/dodamapi/outsleeping/OutSleepingController.java
+++ b/dodam-api/src/main/java/b1nd/dodamapi/outsleeping/OutSleepingController.java
@@ -4,6 +4,7 @@
 import b1nd.dodamapi.common.response.ResponseData;
 import b1nd.dodamcore.outsleeping.application.OutSleepingService;
 import b1nd.dodamcore.outsleeping.application.dto.req.ApplyOutSleepingReq;
+import b1nd.dodamcore.outsleeping.application.dto.req.RejectOutSleepingReq;
 import b1nd.dodamcore.outsleeping.application.dto.res.OutSleepingRes;
 import b1nd.dodamcore.outsleeping.domain.enums.OutSleepingStatus;
 import jakarta.validation.Valid;
@@ -29,21 +30,21 @@ public Response apply(@RequestBody @Valid ApplyOutSleepingReq req) {
 
     @PatchMapping("/{id}/allow")
     public Response allow(@PathVariable Long id) {
-        outSleepingService.modifyStatus(id, OutSleepingStatus.ALLOWED);
+        outSleepingService.modifyStatus(id, OutSleepingStatus.ALLOWED, null);
 
         return Response.noContent("외박 승인 성공");
     }
 
     @PatchMapping("/{id}/reject")
-    public Response reject(@PathVariable Long id) {
-        outSleepingService.modifyStatus(id, OutSleepingStatus.REJECTED);
+    public Response reject(@PathVariable Long id, @RequestBody RejectOutSleepingReq req) {
+        outSleepingService.modifyStatus(id, OutSleepingStatus.REJECTED, req.rejectReason());
 
         return Response.noContent("외박 거절 성공");
     }
 
     @PatchMapping("/{id}/revert")
     public Response revert(@PathVariable Long id) {
-        outSleepingService.modifyStatus(id, OutSleepingStatus.PENDING);
+        outSleepingService.modifyStatus(id, OutSleepingStatus.PENDING, null);
 
         return Response.noContent("외박 대기 성공");
     }
diff --git a/dodam-core/src/main/java/b1nd/dodamcore/nightstudy/application/NightStudyService.java b/dodam-core/src/main/java/b1nd/dodamcore/nightstudy/application/NightStudyService.java
index 09abe94f..4c0f07ec 100644
--- a/dodam-core/src/main/java/b1nd/dodamcore/nightstudy/application/NightStudyService.java
+++ b/dodam-core/src/main/java/b1nd/dodamcore/nightstudy/application/NightStudyService.java
@@ -56,13 +56,13 @@ public void cancel(Long id) {
     }
 
     @Transactional
-    public void modifyStatus(Long id, NightStudyStatus status) {
+    public void modifyStatus(Long id, NightStudyStatus status, String rejectReason) {
         NightStudy nightStudy = nightStudyRepository.findById(id)
                 .orElseThrow(NightStudyNotFoundException::new);
         Teacher teacher = teacherRepository.findByMember(memberSessionHolder.current())
                 .orElseThrow(TeacherNotFoundException::new);
 
-        nightStudy.modifyStatus(teacher, status);
+        nightStudy.modifyStatus(teacher, status, rejectReason);
     }
 
     @Transactional(readOnly = true)
diff --git a/dodam-core/src/main/java/b1nd/dodamcore/nightstudy/domain/entity/NightStudy.java b/dodam-core/src/main/java/b1nd/dodamcore/nightstudy/domain/entity/NightStudy.java
index 203f654d..a66ed95c 100644
--- a/dodam-core/src/main/java/b1nd/dodamcore/nightstudy/domain/entity/NightStudy.java
+++ b/dodam-core/src/main/java/b1nd/dodamcore/nightstudy/domain/entity/NightStudy.java
@@ -55,6 +55,8 @@ public class NightStudy extends BaseEntity {
     @JoinColumn(name = "fk_teacher_id")
     private Teacher teacher;
 
+    private String rejectReason;
+
     @NotNull
     private LocalDate startAt;
 
@@ -78,9 +80,21 @@ public NightStudy(String content, boolean doNeedPhone, String reasonForPhone, Sc
         this.endAt = endAt;
     }
 
-    public void modifyStatus(Teacher teacher, NightStudyStatus status) {
+    public NightStudy(Student student) {
+        this.content = "민규야 힘내. 힘규야 민내.";
+        this.doNeedPhone = false;
+        this.reasonForPhone = null;
+        this.place = SchoolPlace.PROGRAMMING_1;
+        this.status = NightStudyStatus.PENDING;
+        this.student = student;
+        this.startAt = LocalDate.now();
+        this.endAt = LocalDate.now();
+    }
+
+    public void modifyStatus(Teacher teacher, NightStudyStatus status, String rejectReason) {
         this.status = status;
         this.teacher = teacher;
+        this.rejectReason = rejectReason;
     }
 
     public void isApplicant(Student student) {
diff --git a/dodam-core/src/main/java/b1nd/dodamcore/outgoing/application/OutGoingService.java b/dodam-core/src/main/java/b1nd/dodamcore/outgoing/application/OutGoingService.java
index 02c669d4..0d912a68 100644
--- a/dodam-core/src/main/java/b1nd/dodamcore/outgoing/application/OutGoingService.java
+++ b/dodam-core/src/main/java/b1nd/dodamcore/outgoing/application/OutGoingService.java
@@ -38,11 +38,11 @@ public void apply(ApplyOutGoingReq req) {
     }
 
     @Transactional
-    public void modifyStatus(Long id, OutGoingStatus status) {
+    public void modifyStatus(Long id, OutGoingStatus status, String rejectReason) {
         Teacher teacher = teacherRepository.getByMember(memberSessionHolder.current());
         OutGoing outGoing = outGoingRepository.getById(id);
 
-        outGoing.modifyStatus(teacher, status);
+        outGoing.modifyStatus(teacher, status, rejectReason);
     }
 
     @Transactional
diff --git a/dodam-core/src/main/java/b1nd/dodamcore/outgoing/domain/entity/OutGoing.java b/dodam-core/src/main/java/b1nd/dodamcore/outgoing/domain/entity/OutGoing.java
index 4ceb16fb..361811eb 100644
--- a/dodam-core/src/main/java/b1nd/dodamcore/outgoing/domain/entity/OutGoing.java
+++ b/dodam-core/src/main/java/b1nd/dodamcore/outgoing/domain/entity/OutGoing.java
@@ -46,6 +46,8 @@ public class OutGoing extends BaseEntity {
     @JoinColumn(name = "fk_teacher_id")
     private Teacher teacher;
 
+    private String rejectReason;
+
     @Builder
     public OutGoing(String reason, LocalDateTime startAt, LocalDateTime endAt, Student student) {
         isInvalidPeriod(startAt, endAt);
@@ -57,9 +59,10 @@ public OutGoing(String reason, LocalDateTime startAt, LocalDateTime endAt, Stude
         this.student = student;
     }
 
-    public void modifyStatus(Teacher teacher, OutGoingStatus status) {
+    public void modifyStatus(Teacher teacher, OutGoingStatus status, String rejectReason) {
         this.status = status;
         this.teacher = teacher;
+        this.rejectReason = rejectReason;
     }
 
     public void isApplicant(Student student) {
diff --git a/dodam-core/src/main/java/b1nd/dodamcore/outsleeping/application/OutSleepingService.java b/dodam-core/src/main/java/b1nd/dodamcore/outsleeping/application/OutSleepingService.java
index 31504b43..f14ec15f 100644
--- a/dodam-core/src/main/java/b1nd/dodamcore/outsleeping/application/OutSleepingService.java
+++ b/dodam-core/src/main/java/b1nd/dodamcore/outsleeping/application/OutSleepingService.java
@@ -36,11 +36,11 @@ public void apply(ApplyOutSleepingReq req) {
     }
 
     @Transactional
-    public void modifyStatus(Long id, OutSleepingStatus status) {
+    public void modifyStatus(Long id, OutSleepingStatus status, String rejectReason) {
         Teacher teacher = teacherRepository.getByMember(memberSessionHolder.current());
         OutSleeping outSleeping = outSleepingRepository.getById(id);
 
-        outSleeping.modifyStatus(teacher, status);
+        outSleeping.modifyStatus(teacher, status, rejectReason);
     }
 
     @Transactional
diff --git a/dodam-core/src/main/java/b1nd/dodamcore/outsleeping/domain/entity/OutSleeping.java b/dodam-core/src/main/java/b1nd/dodamcore/outsleeping/domain/entity/OutSleeping.java
index 9e39ebf0..411e8327 100644
--- a/dodam-core/src/main/java/b1nd/dodamcore/outsleeping/domain/entity/OutSleeping.java
+++ b/dodam-core/src/main/java/b1nd/dodamcore/outsleeping/domain/entity/OutSleeping.java
@@ -46,6 +46,8 @@ public class OutSleeping extends BaseEntity {
     @JoinColumn(name = "fk_teacher_id")
     private Teacher teacher;
 
+    private String rejectReason;
+
     @Builder
     public OutSleeping(String reason, LocalDate startAt, LocalDate endAt, Student student) {
         isInvalidPeriod(startAt, endAt);
@@ -57,9 +59,10 @@ public OutSleeping(String reason, LocalDate startAt, LocalDate endAt, Student st
         this.student = student;
     }
 
-    public void modifyStatus(Teacher teacher, OutSleepingStatus status) {
+    public void modifyStatus(Teacher teacher, OutSleepingStatus status, String rejectReason) {
         this.status = status;
         this.teacher = teacher;
+        this.rejectReason = rejectReason;
     }
 
     public void isApplicant(Student student) {