diff --git a/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java b/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java
index 5a2e999..3876ffd 100644
--- a/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java
+++ b/app/src/main/java/com/example/tampopo_client/viewmodels/ActivityViewModel.java
@@ -8,9 +8,15 @@
 
 import com.example.tampopo_client.models.Activity;
 import com.example.tampopo_client.resources.ActivitiesResource;
+import com.example.tampopo_client.resources.UserResource;
 
-import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
 
 import retrofit2.Call;
 import retrofit2.Callback;
@@ -18,6 +24,8 @@
 import retrofit2.Retrofit;
 import retrofit2.converter.jackson.JacksonConverterFactory;
 
+// NOTE: MainActivityでLiveDataをobserveし表示する
+
 /**
  * アクティビティを扱うためのViewModel
  *
@@ -26,17 +34,91 @@
  */
 public class ActivityViewModel extends ViewModel {
     private final ActivitiesResource activitiesResource;
+    private final UserResource userResource;
 
-    private final MutableLiveData<List<Activity>> activitiesLiveData;
+    private final MutableLiveData<Map<String, Activity>> activitiesLiveData; // key=userId, value=activity
+    private final MutableLiveData<List<String>> friendUserIdsLiveData;
+
+    private final ScheduledExecutorService fetchActivitiesTaskScheduler;
+    private ScheduledFuture<?> fetchActivitiesTask;
+
+    private final ScheduledExecutorService fetchFriendIdsTaskScheduler;
+    private ScheduledFuture<?> fetchFriendIdsTask;
 
     public ActivityViewModel() {
+        // Retrofitの初期化
         final Retrofit retrofit = new Retrofit.Builder()
                 .baseUrl("http://nitta-lab-www.is.konan-u.ac.jp/tampopo/")
                 .addConverterFactory(JacksonConverterFactory.create())
                 .build();
         activitiesResource = retrofit.create(ActivitiesResource.class);
+        userResource = retrofit.create(UserResource.class);
 
-        activitiesLiveData = new MutableLiveData<>(List.of());
+        // LiveDataの初期化
+        activitiesLiveData = new MutableLiveData<>(Map.of());
+        friendUserIdsLiveData = new MutableLiveData<>(List.of());
+
+        // スケジューラーの作成
+        fetchActivitiesTaskScheduler = Executors.newSingleThreadScheduledExecutor();
+        fetchFriendIdsTaskScheduler = Executors.newSingleThreadScheduledExecutor();
+    }
+
+    @Override
+    protected void onCleared() {
+        super.onCleared();
+
+        // ViewModelの破棄時にタスクを即停止する
+        if (fetchActivitiesTaskScheduler != null) {
+            fetchActivitiesTaskScheduler.shutdownNow();
+        }
+        if (fetchFriendIdsTaskScheduler != null) {
+            fetchFriendIdsTaskScheduler.shutdownNow();
+        }
+    }
+
+    /**
+     * 定期的に最新のアクティビティ一覧を取得・更新する
+     */
+    public void startFetchingLatestActivities() {
+        if (fetchActivitiesTask != null && !fetchActivitiesTask.isDone()) {
+            return;
+        }
+
+        final Runnable task = () -> {
+            if (!friendUserIdsLiveData.isInitialized()) {
+                return;
+            }
+            if (friendUserIdsLiveData.getValue() == null) {
+                return;
+            }
+            for (String userId : friendUserIdsLiveData.getValue()) {
+                pullLatestActivity(userId);
+            }
+        };
+        fetchActivitiesTask = fetchActivitiesTaskScheduler.scheduleWithFixedDelay(task, 0, 1, TimeUnit.SECONDS);
+    }
+
+    /**
+     * 定期的に最新のフレンド一覧を取得・更新する
+     *
+     * @param userId ユーザーID
+     * @param token  ユーザーの認証用トークン
+     */
+    public void startFetchingLatestFriends(String userId, String token) {
+        if (fetchFriendIdsTask != null && !fetchFriendIdsTask.isDone()) {
+            return;
+        }
+
+        final Runnable task = () -> {
+            if (!friendUserIdsLiveData.isInitialized()) {
+                return;
+            }
+
+            pullLatestFriendUserIds(userId, token);
+
+            Log.d(ActivityViewModel.class.getSimpleName(), "Polling friends data from the server.");
+        };
+        fetchFriendIdsTask = fetchFriendIdsTaskScheduler.scheduleWithFixedDelay(task, 0, 1, TimeUnit.SECONDS);
     }
 
     public void createActivity(String userId, String token, String newActivity) {
@@ -52,12 +134,18 @@
                     getActivityCall.enqueue(new Callback<Activity>() {
                         @Override
                         public void onResponse(@NonNull Call<Activity> call, @NonNull Response<Activity> response) {
-                            List<Activity> activities = activitiesLiveData.getValue();
+                            Map<String, Activity> activities = activitiesLiveData.getValue();
                             if (activities == null) {
-                                activities = new ArrayList<>();
+                                activities = new HashMap<>();
                             }
+
                             Activity createdActivity = response.body();
-                            activities.add(createdActivity);
+                            if (activities.containsKey(userId)) {
+                                activities.replace(userId, createdActivity);
+                            } else {
+                                activities.put(userId, createdActivity);
+                            }
+
                             activitiesLiveData.postValue(activities);
                         }
 
@@ -73,12 +161,75 @@
 
             @Override
             public void onFailure(@NonNull Call<String> call, @NonNull Throwable t) {
-                Log.e(ActivityViewModel.class.getSimpleName(), "An error has occurred.", t);
+                Log.e(ActivityViewModel.class.getSimpleName(), "An error has occurred while creating new activity.", t);
             }
         });
     }
 
-    public MutableLiveData<List<Activity>> getActivitiesLiveData() {
+    /**
+     * 最新のユーザーのアクティビティを取得・更新する
+     *
+     * @param userId 取得対象のユーザーのID
+     */
+    private void pullLatestActivity(String userId) {
+        Call<List<Activity>> fetchActivityCall = activitiesResource.getActivities(userId, "LATEST");
+        fetchActivityCall.enqueue(new Callback<List<Activity>>() {
+            @Override
+            public void onResponse(@NonNull Call<List<Activity>> call, @NonNull Response<List<Activity>> response) {
+                if (response.isSuccessful()) {
+                    List<Activity> fetchedActivities = response.body();
+                    if (fetchedActivities != null) {
+                        Activity latestActivity = response.body().get(0);
+                        Map<String, Activity> activities = activitiesLiveData.getValue();
+                        if (activities == null) {
+                            activities = new HashMap<>();
+                        }
+                        if (activities.containsKey(userId)) {
+                            activities.replace(userId, latestActivity);
+                        } else {
+                            activities.put(userId, latestActivity);
+                        }
+
+                        activitiesLiveData.postValue(activities);
+                    }
+                }
+            }
+
+            @Override
+            public void onFailure(@NonNull Call<List<Activity>> call, @NonNull Throwable t) {
+                Log.e(ActivityViewModel.class.getSimpleName(), "An error has occurred while fetching the latest activity.", t);
+            }
+        });
+    }
+
+    /**
+     * 最新の自分のフレンドのユーザーIDをすべて取得・更新する。
+     *
+     * @param userId 自分のユーザーID
+     * @param token  自分のユーザー認証用トークン
+     */
+    private void pullLatestFriendUserIds(String userId, String token) {
+        Call<List<String>> fetchFriendUserIdsCall = userResource.getFriends(userId, token);
+        fetchFriendUserIdsCall.enqueue(new Callback<List<String>>() {
+            @Override
+            public void onResponse(@NonNull Call<List<String>> call, @NonNull Response<List<String>> response) {
+                if (response.isSuccessful()) {
+                    friendUserIdsLiveData.postValue(response.body());
+                }
+            }
+
+            @Override
+            public void onFailure(@NonNull Call<List<String>> call, @NonNull Throwable t) {
+                Log.e(ActivityViewModel.class.getSimpleName(), "An error has occurred while fetching all friends' id.", t);
+            }
+        });
+    }
+
+    public MutableLiveData<Map<String, Activity>> getActivitiesLiveData() {
         return activitiesLiveData;
     }
+
+    public MutableLiveData<List<String>> getFriendUserIdsLiveData() {
+        return friendUserIdsLiveData;
+    }
 }