With an object of allowing steering wheel operation to be carried out easily at a normal time and when an abnormality occurs, the invention includes a motor having two windings and a control unit having two control systems that supply control signals to each winding of the motor and when an abnormality occurs in one winding of the motor or in one system inside the control unit, a supply of current to the winding in which the abnormality has occurred is cut to zero, and the motor is driven by a predetermined current necessary at a normal time being supplied to the other winding, while at a time of a normal drive when no abnormality has occurred, the current supply is shared between the two windings, whereby the motor is driven.