To detect the illegal unlocking of the key of an opening/closing door and/or a game board body even during night when power source is not supplied.

A game machine having an outer frame, the opening/closing door 9 arranged openably to the outer frame, and the game board body has a moving member 301 moving based on the unlocking movement of the key of the opening/closing door and/or the game board body, a position detecting sensor 302 detecting the position of the moving member and detecting whether the moving member is present in a home position or in a moving position, and a determination circuit determining the opening/closing of the opening/closing door 9 and/or the game board body based on the output of the position detecting sensor 302.