A basic assist torque is set on the basis of the vehicle speed and the steering torque, and when the vehicle changes from a straight driving state to a curve driving state, a correction amount for the basic assist torque is calculated, which is to offset steering torque characteristic values which has been predetermined depending on a steering angle, in a direction opposite to the steering direction by correcting an absolute value of the basic assist torque to reduce its action on the steering direction depending at least upon the curvature radius of the driving road in front of the vehicle, and the basic assist torque is corrected with the basic assist torque correction amount and the controlled/corrected torque (assist torque) is output to a motor drive unit.