A voltage adjustment circuit includes switches connected in parallel between a circuit unit and an electric power supply line to which a first electric power supply voltage is applied, and changes the number of switches turned off, based on a comparison result between a target value and a second electric power supply voltage supplied to the circuit unit, to adjust the second electric power supply voltage. A control circuit decides an interval for increasing the number of switches turned off when the circuit unit changes to standby state, based on a leak current value of the circuit unit in standby state, a time in which the second electric power supply voltage changes from a first to a second value, the first and second values, and an electric potential difference by which the second electric power supply voltage changes when one switch switches between on and off.