A digital camera 10 includes a systems control section 20. When the systems control section 20 receives any of operation signals from a key operation section 18, the systems control section 20 measures the passage of time with a timer 22, and continues the time measurement for a specified period of time until any of the operation signals is supplied. In an imaging mode, the system controls section 20 generates an oscillation frequency higher than a normal oscillation frequency with a signal generation circuit 260 in response to a button depressing operation of a release shutter button 180, and generates the normal oscillation frequency upon receipt of any one of the operation signals in a specified period of time. The system controls section 20 continues monitoring the operation signals and generates an oscillation frequency lower than the normal frequency to thereby control to lower the power consumption depending on the result of the measurement of the passage of the specified period of time by the timer 22.