PURPOSE: To prevent the cost from being increased due to the increase of man- hours for adjustments by electrically adjusting the phase shift between an encoder and an excitation phase.

CONSTITUTION: The encoder 2 outputs signals of phases A and B corresponding to the angle of rotation of a pulse motor 1 and a comparator 3 classifies cases corresponding to the signal levels of the phases A and B. Then the pulse motor 1 is rotated in microsteps and the phase shift quantity is detected from the microstep feed quantity up to the point of time of changes of the case-classified signals. On the basis of the phase shift quantity, a controller 4a calculates correction values for currents supplied to the respective phases of the pulse motor 1 and corrected current values are supplied to the pulse motor 1.