PURPOSE: To limit a conducting current in an optimum state at the time of overloading a motor by stopping the conduction of the motor for a predetermined period of time when the current of the motor exceeds a predetermined value.

CONSTITUTION: A torque sensor 3 detects the rotation of a steering wheel and supplies it through a PID compensator 320 and an A/D converter 330 to a CPU 100. A malfunction detector 340 outputs a malfunction signal when the detection torque exceeds an allowable value responsive to a vehicle speed. The CPU 100 pulse-width-modulation controls PET drivers 221-224 in response to the detection torque. On the other hand, a current control unit 230 controls a FET driver OFF for a predetermined time when the current of the motor 8 becomes a predetermined value or more. Thus, the current can be controlled in an optimum state even at the time of overloading.