To provide a power source device for an on-vehicle refrigerator capable of working by drawing a key of a vehicle at a luggage loading or unloading time or a loaded article conveying or delivering work time while maintaining a stable indoor temperature with a simple constitution in an idle-stop loading vehicle or a home delivery or distribution vehicle.

A sub-battery 2 connected to a main battery 1 via an isolator 5 is connected to a power source circuit 12b via an electromagnetic relay 13 having independent contacts of two circuits of a normally closed contact and a normally opened contact. The circuit 12b has a circuit for applying a voltage directly from the normally opened contact, and a circuit for passing a current from the normally closed contact for a prescribed time via a timer circuit 12c. The circuit 12b supplies a power to the circuit 12a of the on-vehicle refrigerator 8 for a prescribed time to drive a vibration type compressor 11.