To provide a game monitoring device adaptable to a small-scale hall at a low cost by simplifying the structure of the game monitoring device collating the inherent ID information stored in a game arithmetic processing unit in advance.

This game monitoring device (ID inspecting device 35) requests the game arithmetic processing unit 200 to send the inherent ID, receives the inherent ID sent in response to the request, stores the received inherent ID in an EEPROM(electrically erasable programmable read-only memory) 37b if no inherent ID is stored in the EEPROM 37b, and compares the received inherent ID with the inherent ID stored in the EEPROM 37b to judge the validity of the game arithmetic processing unit 200 if the inherent ID is stored in the EEPROM 37b.