PURPOSE: To allow a rental locker system provided with an automatic power supply interruption function to correspond to specific business such as all-night operation at the end and beginning of the year.

CONSTITUTION: An external power supply monitoring circuit 17 is connected to the prestage of a power supply circuit in a central control unit 1. The circuit 17 detects the ON/OFF of an external power supply. A microcomputer 14 controls a power supply switch 12. When the external power supply is ON based upon the detection result of the circuit 17, the switch 12 is always held at ON. When the external power supply is turned off and it arrives at interruption time, the switch 12 is turned off. If the external power supply is turned on even before power supply time, the switch 12 is turned on. Even when the external power supply is OFF, the switch 12 is turned on at the arrival of power supply time.