To provide a power supply controller which can cope with a heavy load by achieving an overvoltage protection function through simple circuitry without enlarging a surge absorber.

The power supply controller comprises a control circuit 2 for supplying power from an AC power supply 1 to a load 3 under predetermined control, a power supply relay 5 connected in series with the control circuit, a power switch 4 connected in parallel with the power supply relay, a series circuit of a surge absorber 8 and a fuse 7 connected between the AC power supply and the control circuit in parallel with the control circuit, and a circuit 9 for detecting voltage application from the AC power supply across the surge absorber and inputting the detection output to the control circuit. On condition that voltage application is detected by the AC power supply detection circuit, the control circuit can turn on the power supply relay, and keeps ON state of the power supply relay on condition that voltage application is detected by the AC power supply detection circuit.