To provide a power supply voltage monitoring device of a game machine which is capable of easily and quickly specifying the cause of stoppage of the game machine.

A slot machine 1 (game machine) is provided with the power supply voltage monitoring device 80 for monitoring the voltage of a primary power supply voltage first when a table power switch 28 is turned off and the operation of the slot machine 1 (game machine) is stopped, performing reporting by an LED 830a or 830b for abnormality of a reporting means 83 when the voltage of the primary power supply voltage is abnormal, monitoring the voltage of secondary power supply voltages after the table power switch 28 is restored when the voltage of the primary power supply voltage is normal, performing reporting by one of LEDs 831a, 832a and 833a for the abnormality of the reporting means 83 when the voltage of one of the secondary power supply voltages is abnormal, and performing reporting by LEDs 830c, 831b, 832b and 833b for normality of the reporting means when the primary and second power supply voltages are normal, that is when there is a fault of the slot machine 1 itself.