PURPOSE: To generate no positional shift of a rotor due to the OFF/ON of a power source and position the rotor exactly, by setting exciting phase excited when the power source is recast, to be exciting phase excited when the power source is OFF and on the stop of the rotor.

CONSTITUTION: The CW pulse or CCW pulse of output generated from a pulse generation circuit 2 is directed to an UP/DOWN counter circuit 4 for input, and the number of pulse is counted. The count value of the UP/DOWN counter circuit 4 is battery-backed-up, and the memory is retained, also when a power source is OFF. When the power source is re-cast after it is OFF, then the output of the pulse of a number equal to a step number found from the count value of the counter circuit 4 is directed to a driving circuit 3. As a result, excitation from an excitation step excited when the power source is OFF can be executed.