diff --git a/apps/server/src/domains/room/RoomHandler.ts b/apps/server/src/domains/room/RoomHandler.ts
index 91f4dec..6cb4672 100644
--- a/apps/server/src/domains/room/RoomHandler.ts
+++ b/apps/server/src/domains/room/RoomHandler.ts
@@ -2,24 +2,28 @@
 import { RoomManager } from "./RoomManager";
 import { protocol } from "@repo/shared";
 import type { roomTypes } from "@repo/shared";
+import { executeJoinRoomUseCase } from "./application/useCases/executeJoinRoomUseCase";
+import { executeRoomDisconnectUseCase } from "./application/useCases/executeRoomDisconnectUseCase";
 
 export const registerRoomHandlers = (io: Server, socket: Socket, roomManager: RoomManager) => {
   
   socket.on(protocol.SocketEvents.JOIN_ROOM, (data: roomTypes.JoinRoomPayload) => {
-    const { roomId, playerName } = data;
-    console.log("[RoomHandler] JOIN_ROOM received", { roomId, socketId: socket.id, playerName });
+    const { roomId } = data;
     
     socket.join(roomId);
 
-    // RoomManagerにデータ操作を依頼
-    const room = roomManager.addPlayerToRoom(roomId, socket.id, playerName);
+    executeJoinRoomUseCase({
+      roomManager,
+      socketId: socket.id,
+      data,
+      emitToRoom: (targetRoomId, event, payload) => {
+        if (payload === undefined) {
+          io.to(targetRoomId).emit(event);
+          return;
+        }
 
-    // ルーム内全員向け最新状態配信
-    io.to(roomId).emit(protocol.SocketEvents.ROOM_UPDATE, room);
-    console.log("[RoomHandler] ROOM_UPDATE emitted", {
-      roomId,
-      ownerId: room.ownerId,
-      totalPlayers: room.players.length
+        io.to(targetRoomId).emit(event, payload);
+      },
     });
   });
 
@@ -29,20 +33,16 @@
  * 切断時のルームクリーンアップ処理
  */
 export const handleRoomDisconnect = (io: Server, socket: Socket, roomManager: RoomManager) => {
-  // ルームからの除外処理
-  const updatedRooms = roomManager.removePlayer(socket.id);
-  console.log("[RoomHandler] disconnect cleanup", {
+  executeRoomDisconnectUseCase({
+    roomManager,
     socketId: socket.id,
-    updatedRoomCount: updatedRooms.length
-  });
-  
-  // 更新があったルーム（オーナー変更など）にのみ通知を飛ばす
-  updatedRooms.forEach(room => {
-    io.to(room.roomId).emit(protocol.SocketEvents.ROOM_UPDATE, room);
-    console.log("[RoomHandler] ROOM_UPDATE emitted", {
-      roomId: room.roomId,
-      ownerId: room.ownerId,
-      totalPlayers: room.players.length
-    });
+    emitToRoom: (roomId, event, payload) => {
+      if (payload === undefined) {
+        io.to(roomId).emit(event);
+        return;
+      }
+
+      io.to(roomId).emit(event, payload);
+    },
   });
 };
\ No newline at end of file
diff --git a/apps/server/src/domains/room/application/useCases/executeJoinRoomUseCase.ts b/apps/server/src/domains/room/application/useCases/executeJoinRoomUseCase.ts
new file mode 100644
index 0000000..284f07b
--- /dev/null
+++ b/apps/server/src/domains/room/application/useCases/executeJoinRoomUseCase.ts
@@ -0,0 +1,31 @@
+import { protocol } from "@repo/shared";
+import type { roomTypes } from "@repo/shared";
+import { RoomManager } from "@server/domains/room/RoomManager";
+
+type EmitToRoom = (roomId: string, event: string, payload?: unknown) => void;
+
+type ExecuteJoinRoomUseCaseParams = {
+  roomManager: RoomManager;
+  socketId: string;
+  data: roomTypes.JoinRoomPayload;
+  emitToRoom: EmitToRoom;
+};
+
+export const executeJoinRoomUseCase = ({
+  roomManager,
+  socketId,
+  data,
+  emitToRoom,
+}: ExecuteJoinRoomUseCaseParams) => {
+  const { roomId, playerName } = data;
+  console.log("[RoomHandler] JOIN_ROOM received", { roomId, socketId, playerName });
+
+  const room = roomManager.addPlayerToRoom(roomId, socketId, playerName);
+
+  emitToRoom(roomId, protocol.SocketEvents.ROOM_UPDATE, room);
+  console.log("[RoomHandler] ROOM_UPDATE emitted", {
+    roomId,
+    ownerId: room.ownerId,
+    totalPlayers: room.players.length,
+  });
+};
diff --git a/apps/server/src/domains/room/application/useCases/executeRoomDisconnectUseCase.ts b/apps/server/src/domains/room/application/useCases/executeRoomDisconnectUseCase.ts
new file mode 100644
index 0000000..1b05af1
--- /dev/null
+++ b/apps/server/src/domains/room/application/useCases/executeRoomDisconnectUseCase.ts
@@ -0,0 +1,31 @@
+import { protocol } from "@repo/shared";
+import { RoomManager } from "@server/domains/room/RoomManager";
+
+type EmitToRoom = (roomId: string, event: string, payload?: unknown) => void;
+
+type ExecuteRoomDisconnectUseCaseParams = {
+  roomManager: RoomManager;
+  socketId: string;
+  emitToRoom: EmitToRoom;
+};
+
+export const executeRoomDisconnectUseCase = ({
+  roomManager,
+  socketId,
+  emitToRoom,
+}: ExecuteRoomDisconnectUseCaseParams) => {
+  const updatedRooms = roomManager.removePlayer(socketId);
+  console.log("[RoomHandler] disconnect cleanup", {
+    socketId,
+    updatedRoomCount: updatedRooms.length,
+  });
+
+  updatedRooms.forEach((room) => {
+    emitToRoom(room.roomId, protocol.SocketEvents.ROOM_UPDATE, room);
+    console.log("[RoomHandler] ROOM_UPDATE emitted", {
+      roomId: room.roomId,
+      ownerId: room.ownerId,
+      totalPlayers: room.players.length,
+    });
+  });
+};