diff --git a/src/main/java/com/meetup/teame/backend/domain/activity/entity/Activity.java b/src/main/java/com/meetup/teame/backend/domain/activity/entity/Activity.java
index 63ed6a7..2a58dd5 100644
--- a/src/main/java/com/meetup/teame/backend/domain/activity/entity/Activity.java
+++ b/src/main/java/com/meetup/teame/backend/domain/activity/entity/Activity.java
@@ -80,4 +80,8 @@ public static Activity of(String title, String description, String location, Loc
                 .imageUrl(imageUrl)
                 .build();
     }
+
+    public void incrementCurrentParticipants() {
+        this.currentParticipants++;
+    }
 }
\ No newline at end of file
diff --git a/src/main/java/com/meetup/teame/backend/domain/chatroom/service/ChatRoomService.java b/src/main/java/com/meetup/teame/backend/domain/chatroom/service/ChatRoomService.java
index c044bd0..ae8e748 100644
--- a/src/main/java/com/meetup/teame/backend/domain/chatroom/service/ChatRoomService.java
+++ b/src/main/java/com/meetup/teame/backend/domain/chatroom/service/ChatRoomService.java
@@ -75,18 +75,19 @@ public ReadDirectChatRoomsRes readDirectChatRooms() {
 
     @Transactional
     public Long joinGroupChatRoom(Long activityId) {
+        Activity activity = activityRepository.findById(activityId)
+                .orElseThrow(() -> new CustomException(ExceptionContent.NOT_FOUND_ACTIVITY));
         Long userId = SecurityContextProvider.getAuthenticatedUserId();
         User user = userRepository.findById(userId)
                 .orElseThrow(() -> new CustomException(ExceptionContent.NOT_FOUND_USER));
         GroupChatRoom groupChatRoom = groupChatRoomRepository.findByActivityId(activityId)
                 .orElseGet(() -> {
-                    Activity activity = activityRepository.findById(activityId)
-                            .orElseThrow(() -> new CustomException(ExceptionContent.NOT_FOUND_ACTIVITY));
                     return groupChatRoomRepository.save(GroupChatRoom.of(activity));
                 });
         if (userChatRoomRepository.existsByChatRoomIdAndUserId(groupChatRoom.getId(), user.getId()))
             throw new CustomException(ExceptionContent.BAD_REQUEST_ALREADY_JOIN_CHATROOM);
         userChatRoomRepository.save(UserChatRoom.of(groupChatRoom, user));
+        activity.incrementCurrentParticipants();
         return groupChatRoom.getId();
     }
 
diff --git a/src/main/java/com/meetup/teame/backend/domain/experience/dto/response/ExperienceRes.java b/src/main/java/com/meetup/teame/backend/domain/experience/dto/response/ExperienceRes.java
index db34b82..c29260e 100644
--- a/src/main/java/com/meetup/teame/backend/domain/experience/dto/response/ExperienceRes.java
+++ b/src/main/java/com/meetup/teame/backend/domain/experience/dto/response/ExperienceRes.java
@@ -28,7 +28,7 @@ public static ExperienceRes of(Experience experience) {
                 .age(experience.getUser().getAge())
                 .gender(experience.getUser().getGender().getDescription())
                 .location(experience.getUser().getLocation())
-                .message(experience.getDescription())
+                .message(experience.getDetail())
                 .build();
     }
 }