diff --git a/html/webapp/modules/pm/components/Action.class.php b/html/webapp/modules/pm/components/Action.class.php
index eac672b..64869ce 100755
--- a/html/webapp/modules/pm/components/Action.class.php
+++ b/html/webapp/modules/pm/components/Action.class.php
@@ -276,6 +276,14 @@ function setMessage()
 				if(!$this->_db->updateExecute("uploads", $params, "upload_id", true)) {
 					return false;
 				}
+				//アップロードファイルの参照を複数のメッセージ間で共有可能にする add by horiguchi@horitada.info
+				$messageUploadsParams = array(
+					"message_id" => $message_id,
+					"upload_id" => $upload_id
+				);
+				if(!$this->_db->insertExecute("pm_message_uploads", $messageUploadsParams, true)) {
+					return false;
+				}
 			}
 		}
 
diff --git a/html/webapp/modules/pm/components/View.class.php b/html/webapp/modules/pm/components/View.class.php
index d8ec749..d463d8d 100755
--- a/html/webapp/modules/pm/components/View.class.php
+++ b/html/webapp/modules/pm/components/View.class.php
@@ -1288,14 +1288,22 @@ function getUploadOwner($upload_id = 0){
 	 function &getUploadReaders($upload_id = 0){
 		$readers = array();
 
+		//アップロードファイルの参照を複数のメッセージ間で共有可能にする add by horiguchi@horitada.info
 		$params = array(
+			$upload_id,
 			$upload_id
 		);
-
-		$sql = "SELECT r.receiver_user_id ".
-			   "FROM {pm_message_receiver} as r, {uploads} as u ".
-			   "WHERE u.unique_id = r.message_id ".
-			   "AND u.upload_id = ?";
+		$sql = "( ".
+					"SELECT r.receiver_user_id ".
+					"FROM {pm_message_receiver} r ".
+					"LEFT JOIN {uploads} u ON u.unique_id = r.message_id ".
+					"WHERE u.upload_id = ? ".
+				") UNION ( ".
+					"SELECT r.receiver_user_id ".
+					"FROM {pm_message_receiver} r ". 
+					"LEFT JOIN {pm_message_uploads} mu ON mu.message_id = r.message_id ".
+					"WHERE mu.upload_id = ? ".
+				") ";
 
 		$records = $this->_db->execute($sql, $params, null, null, true, null);
 		if ($records === false) {
diff --git a/html/webapp/modules/pm/install.ini b/html/webapp/modules/pm/install.ini
index 8b90f23..f669a5e 100755
--- a/html/webapp/modules/pm/install.ini
+++ b/html/webapp/modules/pm/install.ini
@@ -1,4 +1,4 @@
-version = "2.4.2.1"
+version = "2.4.2.1-osws20161111"
 action_name="pm_view_main_init"
 delete_action = "pm_action_admin_operation"
 module_update_action="pm_update"
diff --git a/html/webapp/modules/pm/sql/mysql/table.sql b/html/webapp/modules/pm/sql/mysql/table.sql
index a573de5..19682b0 100644
--- a/html/webapp/modules/pm/sql/mysql/table.sql
+++ b/html/webapp/modules/pm/sql/mysql/table.sql
@@ -172,3 +172,11 @@ CREATE TABLE `pm_forward` (
   PRIMARY KEY  (`forward_id`),
   INDEX pm_forward_insert_user_id (insert_user_id)
 ) ENGINE=MyISAM;
+
+-- -
+-- テーブルの構造 `pm_message_uploads`
+-- -
+CREATE TABLE `pm_message_uploads` (
+  `message_id`            int(11) unsigned NOT NULL,
+  `upload_id`             int(11) unsigned NOT NULL
+) ENGINE=MyISAM;
diff --git a/html/webapp/modules/pm/update/Update.class.php b/html/webapp/modules/pm/update/Update.class.php
index 7d0b95e..2cae958 100644
--- a/html/webapp/modules/pm/update/Update.class.php
+++ b/html/webapp/modules/pm/update/Update.class.php
@@ -77,6 +77,21 @@ function execute()
 			$result = $this->db->execute($sql);
 			if($result === false) return false;
 		}
+
+		//アップロードファイルの参照を複数のメッセージ間で共有可能にする add by horiguchi@horitada.info
+		$adodb = $this->db->getAdoDbObject();
+		$metaTables = $adodb->MetaTables();
+		if (!in_array($this->db->getPrefix()."pm_message_uploads", $metaTables)) {
+			$sql = "CREATE TABLE `".$this->db->getPrefix()."pm_message_uploads` (" .
+					"`message_id` int(11) UNSIGNED NOT NULL,".
+					"`upload_id`  int(11) UNSIGNED NOT NULL ".
+					") TYPE=MyISAM;";
+			$result = $this->db->execute($sql);
+			if ($result === false) {
+				return false;
+			}
+		}
+
 		return true;
 	}
 }