To provide a power supply circuit for an on-vehicle equipment, capable of holding its memory content even when the output voltage from a secondary cell (second power source) is reduced below a predetermined value.

The power supply circuit for the on-vehicle equipment comprises an on-vehicle battery 2 for supplying a power to a memory 4, a chargeable battery 8 for charging the power supplied from the battery 2 via an accessory switch (ACC) by a charger 7, a microcomputer 6 for monitoring the output voltage of the battery 8 to control a power supply route, and a switch 5 for switching the power supply route under the control of the microcomputer 6.