With the objective of reducing current consumption of a regulator circuit per se, switches for performing on/off of an operating current are inserted in series with transistors of a reference voltage generating unit and a differential amplifying unit that constitute the regulator circuit. A switch for turning on/off an electrical connection between the reference voltage generating unit and the differential amplifying unit is provided. These switches are periodically on/off-controlled in accordance with a clock signal. Incidentally, when the timing provided to turn on the switch is made faster than the timings provided to turn on the remaining switches, the operation of the differential amplifying unit can be further stabilized.