diff --git a/apps/server/src/domains/game/application/services/GameRoomSession.ts b/apps/server/src/domains/game/application/services/GameRoomSession.ts
index bc77b27..02fdc48 100644
--- a/apps/server/src/domains/game/application/services/GameRoomSession.ts
+++ b/apps/server/src/domains/game/application/services/GameRoomSession.ts
@@ -3,7 +3,11 @@
  * 1ルーム分のゲーム進行状態とゲームループ実行を管理する
  */
 import { logEvent } from "@server/logging/logger";
-import { gameDomainLogEvents, logResults, logScopes } from "@server/logging/index";
+import {
+  gameDomainLogEvents,
+  logResults,
+  logScopes,
+} from "@server/logging/index";
 import type { gameTypes } from "@repo/shared";
 import { GameLoop } from "../../loop/GameLoop";
 import { Player } from "../../entities/player/Player.js";
@@ -14,6 +18,9 @@
   setPlayerPosition,
 } from "../../entities/player/playerMovement.js";
 
+// 💡 追加: チーム割り当てサービスをインポート
+import { TeamAssignmentService } from "../services/TeamAssignmentService.js";
+
 /** ルーム単位のゲーム状態とループ進行を保持するセッションクラス */
 export class GameRoomSession {
   private players: Map<string, Player>;
@@ -21,12 +28,22 @@
   private gameLoop: GameLoop | null = null;
   private startTime: number | undefined;
 
-  constructor(private roomId: string, playerIds: string[]) {
+  constructor(
+    private roomId: string,
+    playerIds: string[],
+  ) {
     this.players = new Map();
     this.mapStore = new MapStore();
 
     playerIds.forEach((playerId) => {
-      const player = createSpawnedPlayer(playerId);
+      // 💡 追加: 現在の this.players (生成済みのプレイヤー達) を見て、一番人数の少ないチームを算出する
+      const assignedTeamId = TeamAssignmentService.getBalancedTeamId(
+        this.players,
+      );
+
+      // 💡 修正: バランス良く割り当てられたチームIDを渡してプレイヤーを生成する
+      const player = createSpawnedPlayer(playerId, assignedTeamId);
+
       this.players.set(playerId, player);
     });
   }
@@ -34,7 +51,7 @@
   public start(
     tickRate: number,
     onTick: (data: gameTypes.TickData) => void,
-    onGameEnd: () => void
+    onGameEnd: () => void,
   ): void {
     if (this.gameLoop) {
       return;
@@ -50,7 +67,7 @@
       () => {
         this.dispose();
         onGameEnd();
-      }
+      },
     );
 
     this.gameLoop.start();
@@ -97,17 +114,11 @@
     return this.players.has(id);
   }
 
-  public getPlayerIds(): string[] {
-    return Array.from(this.players.keys());
-  }
-
-  public isEmpty(): boolean {
-    return this.players.size === 0;
-  }
-
   public dispose(): void {
-    this.gameLoop?.stop();
-    this.gameLoop = null;
-    this.startTime = undefined;
+    if (this.gameLoop) {
+      this.gameLoop.stop();
+      this.gameLoop = null;
+    }
+    this.players.clear();
   }
-}
\ No newline at end of file
+}
diff --git a/apps/server/src/domains/game/application/services/TeamAssignmentService.ts b/apps/server/src/domains/game/application/services/TeamAssignmentService.ts
new file mode 100644
index 0000000..8108586
--- /dev/null
+++ b/apps/server/src/domains/game/application/services/TeamAssignmentService.ts
@@ -0,0 +1,36 @@
+/**
+ * TeamAssignmentService
+ * プレイヤーのチーム割り当てロジックを提供するサービス
+ */
+import { config } from "@repo/shared";
+import type { Player } from "../../entities/player/Player.js";
+
+export class TeamAssignmentService {
+  /**
+   * 現在のプレイヤー状況から、最も人数が少ないチームIDを算出する
+   */
+  public static getBalancedTeamId(currentPlayers: Map<string, Player>): number {
+    const teamCount = config.GAME_CONFIG.TEAM_COLORS.length;
+    const teamPopulations = new Array(teamCount).fill(0);
+
+    // 現在の各チームの所属人数を数え上げる
+    for (const player of currentPlayers.values()) {
+      if (player.teamId >= 0 && player.teamId < teamCount) {
+        teamPopulations[player.teamId]++;
+      }
+    }
+
+    // 最も人数が少ないチームを探す
+    let minPopulation = Infinity;
+    let targetTeamId = 0;
+
+    for (let i = 0; i < teamCount; i++) {
+      if (teamPopulations[i] < minPopulation) {
+        minPopulation = teamPopulations[i];
+        targetTeamId = i; // 人数が一番少ないチームIDを記録
+      }
+    }
+
+    return targetTeamId;
+  }
+}
diff --git a/apps/server/src/domains/game/entities/player/Player.ts b/apps/server/src/domains/game/entities/player/Player.ts
index 68a033e..d0f0467 100644
--- a/apps/server/src/domains/game/entities/player/Player.ts
+++ b/apps/server/src/domains/game/entities/player/Player.ts
@@ -3,21 +3,17 @@
  * サーバー側で保持するプレイヤー状態モデルを定義する
  */
 import type { playerTypes } from "@repo/shared";
-import { config } from "@repo/shared";
+// configのimportは不要になります
 
-// サーバー側保持プレイヤー状態モデル
-/** サーバー側プレイヤー座標と所属チームを保持するエンティティ */
 export class Player implements playerTypes.PlayerData {
   public id: string;
   public x: number = 0;
   public y: number = 0;
   public teamId: number;
 
-  constructor(id: string) {
+  // 💡 コンストラクタで teamId を受け取るように変更
+  constructor(id: string, teamId: number) {
     this.id = id;
-    
-    // GAME_CONFIGからチーム数を動的に取得して割り当て
-    const teamCount = config.GAME_CONFIG.TEAM_COLORS.length;
-    this.teamId = Math.floor(Math.random() * teamCount);
+    this.teamId = teamId;
   }
-}
\ No newline at end of file
+}
diff --git a/apps/server/src/domains/game/entities/player/playerSpawn.ts b/apps/server/src/domains/game/entities/player/playerSpawn.ts
index b17e88c..f368069 100644
--- a/apps/server/src/domains/game/entities/player/playerSpawn.ts
+++ b/apps/server/src/domains/game/entities/player/playerSpawn.ts
@@ -6,47 +6,39 @@
 import { Player } from "./Player.js";
 
 /** プレイヤーを生成し，初期スポーン座標を設定して返す */
-// 💡 引数は元通り `id` だけでOKです！
-export const createSpawnedPlayer = (id: string): Player => {
-  // ここで Player が作られ、同時に player.teamId も自動で決まります！
-  const player = new Player(id);
+// 💡 引数に teamId を追加
+export const createSpawnedPlayer = (id: string, teamId: number): Player => {
+  const player = new Player(id, teamId); // ここにteamIdを渡す！
 
   const { GRID_COLS, GRID_ROWS } = config.GAME_CONFIG;
 
-  // 1. チームごとの基準点を決める
   let baseX = GRID_COLS / 2;
   let baseY = GRID_ROWS / 2;
 
-  // 💡 自動で決まった teamId を使って、四隅に振り分ける
   switch (player.teamId % 4) {
-    case 0: // チーム0: 左上
+    case 0: // 左上
       baseX = 2;
       baseY = 2;
       break;
-    case 1: // チーム1: 右下
+    case 1: // 右下
       baseX = GRID_COLS - 2;
       baseY = GRID_ROWS - 2;
       break;
-    case 2: // チーム2: 右上
+    case 2: // 右上
       baseX = GRID_COLS - 2;
       baseY = 2;
       break;
-    case 3: // チーム3: 左下
+    case 3: // 左下
       baseX = 2;
       baseY = GRID_ROWS - 2;
       break;
   }
 
-  // 2. 完全に同じ座標に重ならないように、少しランダムに散らす（±1マスの範囲）
   const scatterX = (Math.random() - 0.5) * 2;
   const scatterY = (Math.random() - 0.5) * 2;
 
-  player.x = baseX + scatterX;
-  player.y = baseY + scatterY;
-
-  // マップ外（壁の中）にはみ出さないように制限（クランプ）
-  player.x = Math.max(1, Math.min(GRID_COLS - 1, player.x));
-  player.y = Math.max(1, Math.min(GRID_ROWS - 1, player.y));
+  player.x = Math.max(1, Math.min(GRID_COLS - 1, baseX + scatterX));
+  player.y = Math.max(1, Math.min(GRID_ROWS - 1, baseY + scatterY));
 
   return player;
 };