To effectively prevent illegality by instantaneously discovering an illegal act in a Pachinko (Japanese pinball game) machine such as the one for erroneously operating an electronic control circuit substrate through the use of electromagnetic wave so as to permit a big hit to occur.

The electronic control circuit substrate 4 where electronic part such as a central processing unit controlling game contents and storage element, or the like, are mounted is arranged on the rear surface of a game machine and the substrate is covered by a transparent case 8 in the Pachinko machine. The machine is provided with a receiver/transmitter 10 transmitting an abnormality detecting signal by radio wave when electromagnetic wave to permit the substrate to execute an erroneous operation is received, which is arranged at the inner side of the transparent case 8, and also a relay equipment 15 executing announcement to an external part through a telephone line when the abnormality detecting signal transmitted from the receiver/transmitter 10 is received is arranged in a game place.