According to an aspect of the present invention, when the CMOS imaging element is out of control, the soft reset and the device reset which partially initialize the CMOS imaging element are sequentially performed before the CMOS imaging element is reset by stopping the power supply where it takes long before the CMOS imaging element is restored. Thus, when the CMOS imaging element is restored to a normal state by one of the reset steps, the time to restore the CMOS imaging element can be substantially reduced.