A power controller includes a digital control circuit which performs a digital control on a basis of a difference between an output voltage supplied to a power control target device and a voltage reference, so that the output voltage is equal to the voltage reference, and a processor control circuit which conducts an operation of a processor in the digital control circuit, in response to a change of a control signal supplied by the power control target device and indicating a state of a load in the power control target device, which monitors an output from the digital control circuit, and which stops the operation of the processor when the load is judged to have no change.