To provide a power supply controller which can accurately control the power supply to a load, with a simple hardware constitution.

A controller comprises a switch 119 which determines power supply from a power source 101 to a load 103, a semiconductor switch 107, which controls power supply from the power source 101 to the load 103 with switching operation while the switch 119 is in operation, a current detection circuit 109 which detects a load current applied to a shunt resistor 105 and outputs a signal showing the state of the load current and a processing circuit 111, which controls the switching operation of the semiconductor switch 107, according to a signal supplied from the power source via the switch 119 and the signal from the current detection circuit 109. The switching operation of the semiconductor switch 107 is controlled with only the hardware.