A power supply control circuit for controlling a power supply circuit having a DC/DC converter is provided. A discharge circuit operates based on a discharge instruction signal for instructing discharge and uses a switching element to remove charges of a capacitor connected to an output terminal of the DC/DC converter. An overvoltage detecting circuit outputs a detection signal when a potential at the output terminal of the DC/DC converter exceeds a predetermined potential. A level conversion circuit outputs a signal obtained by converting a potential applied to the switching element of the discharge circuit. A logic circuit performs a logic operation between an inverted signal of a start-up signal, the detection signal, and the signal obtained by converting the potential, and outputs a failure detection signal representing a failed state of the power supply circuit.