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 08364f9..a361397 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
@@ -12,6 +12,7 @@
 import java.time.LocalDateTime;
 import java.time.format.DateTimeFormatter;
 import java.util.ArrayList;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 
@@ -40,6 +41,8 @@
 
     private final List<UserActivityStatusChangeListener> userActivityStatusChangeListeners;
 
+    private final List<String> sortedFriendUserIds = new ArrayList<>();
+
     /**
      * ActivityのViewModelを作成する。
      *
@@ -117,9 +120,29 @@
                 }
             }
 
-            // 最新のフレンドのユーザーIDを取得して更新する
             if (friendUserIdsLiveData.isInitialized()) {
+                // 最新のフレンドのユーザーIDを取得して更新する
                 pullLatestFriendUserIds(myUserId, myToken);
+
+                // フレンドのIDをアクティビティ更新順に並べ替える
+                List<String> friendUserIds = friendUserIdsLiveData.getValue();
+                List<Friend> friends = new ArrayList<>();
+
+                assert friendUserIds != null;
+                friendUserIds.forEach(userId -> {
+                    List<Activity> activities = getActivitiesLiveDataFromUserId(userId).getValue();
+                    if (activities == null || activities.isEmpty()) {
+                        return;
+                    }
+
+                    Activity latestActivity = activities.get(0);
+                    friends.add(new Friend(userId, latestActivity.getUpdateTime()));
+                });
+                friends.sort(new Friend.UpdateTimeComparator());
+
+                // 並び替えたフレンドのユーザーIDを順番に格納して更新する
+                sortedFriendUserIds.clear();
+                friends.forEach(friend -> sortedFriendUserIds.add(friend.getUserId()));
             }
         };
     }
@@ -238,7 +261,7 @@
      * @param dateTime 変換対象の日時（文字列）
      * @return 変換後の日時（LocalDateTime）
      */
-    private LocalDateTime getDateTimeFromString(String dateTime) {
+    private static LocalDateTime getDateTimeFromString(String dateTime) {
         DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm");
         return LocalDateTime.parse(dateTime, formatter);
     }
@@ -266,13 +289,6 @@
         });
     }
 
-    /**
-     *
-     */
-    private void sortFriendsByLatestUpdateTime() {
-
-    }
-
     public MutableLiveData<Activity> getMyLatestActivityLiveData() {
         return myLatestActivityLiveData;
     }
@@ -299,6 +315,10 @@
         return myToken;
     }
 
+    public List<String> getSortedFriendUserIds() {
+        return sortedFriendUserIds;
+    }
+
     public void addActivityStatusChangeObserver(UserActivityStatusChangeListener observer) {
         userActivityStatusChangeListeners.add(observer);
     }
@@ -307,6 +327,31 @@
         userActivityStatusChangeListeners.clear();
     }
 
+    private static class Friend {
+        private final String userId;
+        private final LocalDateTime latestUpdateTime;
+
+        public Friend(String userId, String latestUpdateTime) {
+            this.userId = userId;
+            this.latestUpdateTime = getDateTimeFromString(latestUpdateTime);
+        }
+
+        public String getUserId() {
+            return userId;
+        }
+
+        public LocalDateTime getLatestUpdateTime() {
+            return latestUpdateTime;
+        }
+
+        public static class UpdateTimeComparator implements Comparator<Friend> {
+            @Override
+            public int compare(Friend o1, Friend o2) {
+                return o1.getLatestUpdateTime().compareTo(o2.getLatestUpdateTime());
+            }
+        }
+    }
+
     private interface ActivityFetchCallback {
         void onSuccess(Activity activity);