The present invention aims to prevent a nonrotation state from being brought about even when a drive allowance is changed by variations in a stepping motor or the like. A pulse down counter circuit outputs pulse down control signal for subjecting main drive pulse to control pulse down when time is counted for a predetermined time period. When a detecting signal exceeding a reference threshold voltage detected by a rotation detecting circuit is detected at a first detection section at start of a rotation detecting time period, a control circuit resets the pulse down counter circuit. Thereby, a main drive pulse generating circuit is not subjected to control pulse down by the pulse down counter circuit, and therefore, it is prevented that the main drive pulse is subjected to pulse down unnecessarily.