diff --git a/apps/server/src/domains/game/GameManager.ts b/apps/server/src/domains/game/GameManager.ts
index 97ef4cf..4bbc1f7 100644
--- a/apps/server/src/domains/game/GameManager.ts
+++ b/apps/server/src/domains/game/GameManager.ts
@@ -66,8 +66,15 @@
     return this.playerRegistry.getAllPlayers();
   }
 
+  // 指定ID配列のプレイヤーを取得
+  getPlayersByIds(playerIds: string[]) {
+    return playerIds
+      .map((playerId) => this.playerRegistry.getPlayer(playerId))
+      .filter((player): player is Player => player !== undefined);
+  }
+
   // 【一時的】移動したプレイヤーの足元を塗り、差分を返すメソッド
-  public paintAndGetUpdates(playerId: string): gridMapTypes.CellUpdate[] {
-    return this.gameSessionService.paintAndGetUpdates(playerId);
+  public paintAndGetUpdates(roomId: string, playerId: string): gridMapTypes.CellUpdate[] {
+    return this.gameSessionService.paintAndGetUpdates(roomId, playerId);
   }
 }
\ No newline at end of file
diff --git a/apps/server/src/domains/game/application/ports/gameUseCasePorts.ts b/apps/server/src/domains/game/application/ports/gameUseCasePorts.ts
index bbeb4f2..851750a 100644
--- a/apps/server/src/domains/game/application/ports/gameUseCasePorts.ts
+++ b/apps/server/src/domains/game/application/ports/gameUseCasePorts.ts
@@ -13,7 +13,7 @@
 }
 
 export interface ReadyForGamePort {
-  getAllPlayers(): playerTypes.PlayerData[];
+  getPlayersByIds(playerIds: string[]): playerTypes.PlayerData[];
   getRoomStartTime(roomId: string): number | undefined;
 }
 
diff --git a/apps/server/src/domains/game/application/services/GameSessionService.ts b/apps/server/src/domains/game/application/services/GameSessionService.ts
index d91ee70..83ae1f3 100644
--- a/apps/server/src/domains/game/application/services/GameSessionService.ts
+++ b/apps/server/src/domains/game/application/services/GameSessionService.ts
@@ -6,12 +6,12 @@
 import { logEvent } from "@server/logging/logEvent";
 
 export class GameSessionService {
-  private mapStore: MapStore;
+  private mapStores: Map<string, MapStore>;
   private gameLoops: Map<string, GameLoop>;
   private roomStartTimes: Map<string, number>;
 
   constructor(private players: Map<string, Player>) {
-    this.mapStore = new MapStore();
+    this.mapStores = new Map();
     this.gameLoops = new Map();
     this.roomStartTimes = new Map();
   }
@@ -37,17 +37,20 @@
 
     const tickRate = config.GAME_CONFIG.PLAYER_POSITION_UPDATE_MS;
     this.roomStartTimes.set(roomId, Date.now());
+    const mapStore = this.mapStores.get(roomId) ?? new MapStore();
+    this.mapStores.set(roomId, mapStore);
 
     const loop = new GameLoop(
       roomId,
       tickRate,
       playerIds,
       this.players,
-      this.mapStore,
+      mapStore,
       onTick,
       () => {
         this.roomStartTimes.delete(roomId);
         this.gameLoops.delete(roomId);
+        this.mapStores.delete(roomId);
         onGameEnd();
       }
     );
@@ -68,6 +71,7 @@
       loop.stop();
       this.gameLoops.delete(roomId);
       this.roomStartTimes.delete(roomId);
+      this.mapStores.delete(roomId);
       logEvent("GameSessionService", {
         event: "STOP_GAME_LOOP",
         result: "stopped",
@@ -82,15 +86,18 @@
     }
   }
 
-  public paintAndGetUpdates(playerId: string): gridMapTypes.CellUpdate[] {
+  public paintAndGetUpdates(roomId: string, playerId: string): gridMapTypes.CellUpdate[] {
+    const mapStore = this.mapStores.get(roomId);
+    if (!mapStore) return [];
+
     const player = this.players.get(playerId);
     if (!player) return [];
 
     const gridIndex = gridMapLogic.getGridIndexFromPosition(player.x, player.y);
     if (gridIndex !== null) {
-      this.mapStore.paintCell(gridIndex, player.teamId);
+      mapStore.paintCell(gridIndex, player.teamId);
     }
 
-    return this.mapStore.getAndClearUpdates();
+    return mapStore.getAndClearUpdates();
   }
 }
diff --git a/apps/server/src/domains/game/application/useCases/readyForGameUseCase.ts b/apps/server/src/domains/game/application/useCases/readyForGameUseCase.ts
index dfae3fd..1084d78 100644
--- a/apps/server/src/domains/game/application/useCases/readyForGameUseCase.ts
+++ b/apps/server/src/domains/game/application/useCases/readyForGameUseCase.ts
@@ -5,6 +5,7 @@
 type ReadyForGameUseCaseParams = {
   socketId: string;
   roomId?: string;
+  playerIds: string[];
   gameManager: ReadyForGamePort;
   publishCurrentPlayers: (players: playerTypes.PlayerData[]) => void;
   publishGameStart: (payload: { startTime: number }) => void;
@@ -13,19 +14,20 @@
 export const readyForGameUseCase = ({
   socketId,
   roomId,
+  playerIds,
   gameManager,
   publishCurrentPlayers,
   publishGameStart,
 }: ReadyForGameUseCaseParams) => {
-  const allPlayers = gameManager.getAllPlayers();
-  publishCurrentPlayers(allPlayers);
+  const roomPlayers = gameManager.getPlayersByIds(playerIds);
+  publishCurrentPlayers(roomPlayers);
 
   logEvent("GameUseCase", {
     event: "READY_FOR_GAME",
     result: "received",
     socketId,
     roomId,
-    totalPlayers: allPlayers.length,
+    totalPlayers: roomPlayers.length,
   });
 
   if (!roomId) {
diff --git a/apps/server/src/domains/room/RoomManager.ts b/apps/server/src/domains/room/RoomManager.ts
index 7dc2152..4197846 100644
--- a/apps/server/src/domains/room/RoomManager.ts
+++ b/apps/server/src/domains/room/RoomManager.ts
@@ -35,4 +35,14 @@
   public getRoomByOwnerId(ownerId: string): roomTypes.Room | undefined {
     return this.roomQueryService.getRoomByOwnerId(ownerId);
   }
+
+  // ルームIDからルームを取得する
+  public getRoomById(roomId: string): roomTypes.Room | undefined {
+    return this.roomQueryService.getRoomById(roomId);
+  }
+
+  // プレイヤーIDから所属ルームを取得する
+  public getRoomByPlayerId(playerId: string): roomTypes.Room | undefined {
+    return this.roomQueryService.getRoomByPlayerId(playerId);
+  }
 }
\ No newline at end of file
diff --git a/apps/server/src/domains/room/application/services/RoomQueryService.ts b/apps/server/src/domains/room/application/services/RoomQueryService.ts
index 89abc7c..6881df8 100644
--- a/apps/server/src/domains/room/application/services/RoomQueryService.ts
+++ b/apps/server/src/domains/room/application/services/RoomQueryService.ts
@@ -8,6 +8,20 @@
 export class RoomQueryService {
   constructor(private rooms: Map<string, roomTypes.Room>) {}
 
+  public getRoomById(roomId: string): roomTypes.Room | undefined {
+    return this.rooms.get(roomId);
+  }
+
+  public getRoomByPlayerId(playerId: string): roomTypes.Room | undefined {
+    for (const room of this.rooms.values()) {
+      if (room.players.some((player) => player.id === playerId)) {
+        return room;
+      }
+    }
+
+    return undefined;
+  }
+
   public getRoomByOwnerId(ownerId: string): roomTypes.Room | undefined {
     for (const room of this.rooms.values()) {
       if (room.ownerId === ownerId) {
diff --git a/apps/server/src/network/handlers/game/createGameEventPublisher.ts b/apps/server/src/network/handlers/game/createGameEventPublisher.ts
index c8b1927..8d36b1e 100644
--- a/apps/server/src/network/handlers/game/createGameEventPublisher.ts
+++ b/apps/server/src/network/handlers/game/createGameEventPublisher.ts
@@ -5,7 +5,7 @@
 import { Server } from "socket.io";
 import { protocol } from "@repo/shared";
 import type { gridMapTypes, playerTypes, roomTypes } from "@repo/shared";
-import { createEmitToAll } from "@server/network/adapters/socketEmitters";
+import { createEmitToRoom } from "@server/network/adapters/socketEmitters";
 import type { CommonHandlerContext } from "../CommonHandler";
 
 type RoomId = roomTypes.Room["roomId"];
@@ -29,7 +29,7 @@
 
 /** 切断時に配信するゲームイベントの送信インターフェース */
 export type GameDisconnectPublisher = {
-  publishPlayerRemovedToAll: (removedPlayerId: SocketId) => void;
+  publishPlayerRemovedToRoom: (roomId: RoomId, removedPlayerId: SocketId) => void;
 };
 
 /** 共通送信コンテキストからゲームイベント送信関数群を生成する */
@@ -61,11 +61,11 @@
 
 /** ゲーム切断時の送信関数群を生成する */
 export const createGameDisconnectPublisher = (io: Server): GameDisconnectPublisher => {
-  const emitToAll = createEmitToAll(io);
+  const emitToRoom = createEmitToRoom(io);
 
   return {
-    publishPlayerRemovedToAll: (removedPlayerId: SocketId) => {
-      emitToAll(protocol.SocketEvents.REMOVE_PLAYER, removedPlayerId);
+    publishPlayerRemovedToRoom: (roomId: RoomId, removedPlayerId: SocketId) => {
+      emitToRoom(roomId, protocol.SocketEvents.REMOVE_PLAYER, removedPlayerId);
     },
   };
 };
diff --git a/apps/server/src/network/handlers/game/handleGameDisconnect.ts b/apps/server/src/network/handlers/game/handleGameDisconnect.ts
index 3cb2c11..0a7be66 100644
--- a/apps/server/src/network/handlers/game/handleGameDisconnect.ts
+++ b/apps/server/src/network/handlers/game/handleGameDisconnect.ts
@@ -11,6 +11,7 @@
 export const handleGameDisconnect = (
   io: Server,
   gameManager: GameManager,
+  roomId: string | undefined,
   playerId: string
 ) => {
   const gameDisconnectPublisher = createGameDisconnectPublisher(io);
@@ -18,6 +19,12 @@
   disconnectUseCase({
     gameManager,
     playerId,
-    publishPlayerRemoved: gameDisconnectPublisher.publishPlayerRemovedToAll,
+    publishPlayerRemoved: (removedPlayerId) => {
+      if (!roomId) {
+        return;
+      }
+
+      gameDisconnectPublisher.publishPlayerRemovedToRoom(roomId, removedPlayerId);
+    },
   });
 };
diff --git a/apps/server/src/network/handlers/game/registerGameHandlers.ts b/apps/server/src/network/handlers/game/registerGameHandlers.ts
index 29d3511..859a451 100644
--- a/apps/server/src/network/handlers/game/registerGameHandlers.ts
+++ b/apps/server/src/network/handlers/game/registerGameHandlers.ts
@@ -59,10 +59,14 @@
   // 参加者の準備完了通知を受けて現在状態を返す
   socket.on(protocol.SocketEvents.READY_FOR_GAME, () => {
     const roomId = Array.from(socket.rooms).find((room) => room !== socket.id);
+    const playerIds = roomId
+      ? (roomManager.getRoomById(roomId)?.players ?? []).map((p) => p.id)
+      : [];
 
     readyForGameUseCase({
       socketId: socket.id,
       roomId,
+      playerIds,
       gameManager,
       publishCurrentPlayers: gamePublisher.publishCurrentPlayersToSocket,
       publishGameStart: gamePublisher.publishGameStartToSocket,
diff --git a/apps/server/src/network/handlers/registerConnectionHandlers.ts b/apps/server/src/network/handlers/registerConnectionHandlers.ts
index 690c439..88a7fac 100644
--- a/apps/server/src/network/handlers/registerConnectionHandlers.ts
+++ b/apps/server/src/network/handlers/registerConnectionHandlers.ts
@@ -41,7 +41,8 @@
         socketId: socket.id,
       });
 
-      handleGameDisconnect(io, gameManager, socket.id);
+      const roomId = roomManager.getRoomByPlayerId(socket.id)?.roomId;
+      handleGameDisconnect(io, gameManager, roomId, socket.id);
       handleRoomDisconnect(io, socket, roomManager);
     });
   });