PURPOSE: To eliminate aggravation of steering response till reaching a stationary state, which occurs when front wheel auxiliary steering is performed according to steering effort.

CONSTITUTION: When front wheels 1L, 1R are mainly steered by a steering wheel 3 via a steering gear 2, a valve 5 auxiliary steers the front wheels 1L, 1R via an actuator 16 by auxiliary steering angle according to flow rate and steering effort from a valve 13 with a delay according to opening of a variable throttle 17. A controller 18 decides flow rate of the valve 13 and opening of the variable throttle 17 based on vehicle speed V detected in a sensor 19, auxiliary steering is excited with a delay in the decreasing direction of the front wheel steering angle thereby, and aggravation of steering response is eliminated by enlarging this auxiliary steering and delay according to increase in a vehicle speed.