To detect the continuity of using a plurality of game machines concurrently by simple constitution.

A CPU 1020 detects the state of game mediums supplied in an upper tray while a player does not play a game to judge whether this state has continued for a prescribed period to detect using of a plurality of game machines concurrently by simple constitution. Then, the CPU 1200 informs the player of information including a machine number with voice in the case of judging that this state continues for the prescribed period, to warn the player. Furthermore, for the second prescribed period after informing with voice, the CPU 1200 judges whether this state continues or not, and prohibits playing by this game machine in the case of judging that this state has continued for the second prescribed period. Thus, it is possible to prevent using a plurality of game machines concurrently without prohibiting playing by this game machine suddenly.