To properly restrain a steering reaction force so as to improve a steering feeling in an active steering system with a superposition transmission by increasingly or decreasingly controlling an operation torque strength according to a jumped up value of an additional steering angle by an electric servo motor when it occurs.

A steering wheel angle δL of a steering mechanism steered by a steering wheel 31 of a vehicle 35 is detected by a steering wheel angle sensor 38, and the detection value is inputted to an open-close loop control unit 37. An additional steering angle δM by an electric servo motor 33 is superposed on the angle δL at a transmission 32, and the superposed angle δL' is fed to a steering gear box 34. At this time, when a jump occurs in a target value of the angle δM, such control is made that the steering torque strength is reduced if there is no dangerous condition in the running dynamic aspect, while it is increased if there is a dangerous condition.