To detect the use of a mode checker in a play at first after power is switched on, and to inform everyone of the use of the mode checker by reporting it as an error using a display part of a game machine.

A main control device 20A is provided with: a storage means of advantages game transfer, which stores transferring to the advantageous game or turning ready to transfer to the advantageous game; and an output means of advantageous game transfer storing signal, which outputs an advantageous game transfer storing signal to an auxiliary control device at every game. The auxiliary control device 20B is provided with a storage means of prize winning signal reception, which stores reception when a prize winning signal is received. If the advantageous game transfer storing signal is received when no reception is stored in the storage means of prize winning signal reception, error display is performed for indicating abnormality of a game machine.