In a game system, a server apparatus (3) that communicates with a plurality of game devices (1) stores play data elements for a plurality of players and public IDs for identifying a plurality of players in a latest play data table (T1) and a public ID table (T2). The server apparatus (3) transmits to a mobile terminal (4), which is being used by a player, information depending on latest play data elements stored in the latest play data table (T1), the latest play data elements belonging to other players who have been registered with the personal relationship table (T3) as a friend of the player possessing the mobile terminal (4). Upon receiving a public-ID-change request from a mobile terminal (4), which is being used by a player, the server apparatus (3) changes the public ID of the player stored in the public ID table (T2).