A control circuit selects a drive pulse group corresponding to the detected voltage of a power cell from among plural drive pulse groups each including plural types of main drive pulses, and selects a drive pulse according to the detected condition of rotation of a stepping motor from among main drive pulses included in the selected drive pulse group or a correction drive pulse having larger energy than the main drive pulses. When the control circuit selects a main drive pulse initially by selecting the drive pulse group, the control circuit selects the main drive pulse having the largest energy in the selected drive pulse group. A drive pulse group selection circuit drives the stepping motor by the main drive pulse in the drive pulse group selected by the control circuit or the correction drive pulse via a main drive pulse output circuit and a correction drive pulse output circuit.