PURPOSE: To detect a motor current without providing a circuit for judgment of current polarity anew.

CONSTITUTION: A current supplied to a motor 1 is controlled by an H bridge. The H bridge is composed of field effect transistors QUL, QUR, QDL, and QDR to each of which a parasitic diode is connected. Moreover, a current detector 5 for detecting the magnitude or the direction of the motor 1 is provided in a power supply line. The absolute value of the motor current MI is gotten by the current detector 5, and the direction of the motor current is gotten by the gate signal supplied to the gates of the field effect transistors QUL, QUR, QDL, and QDR.