PURPOSE: To prevent a load colapse or the like by determining a target rear wheel steering angle arithmetically compounded in accordance with a decrease of detected car height so as to increase a compound rate of the first detection condition quantity further so as to decrease a compound rate of the second detection condition quantity.

CONSTITUTION: In case of no load further with no passenger except a driver, because height of a vehicle in its stopping, detected by a car height detecting means 3, is increased, a target rear wheel steering angle determining means 4 determines a target rear wheel steering angle decreasing its first condition quantity component and increasing the second condition quantity component, and responsibility is advanced corresponding to steering of a front wheel FW. On the contrary, when the load or the passenger except the driver is increased, because the car height decreases, the target rear wheel steering angel, determined by the target rear wheel steering angle determining means 4, increases the first condition quantity component and decreases the second condition quantity component, and decreasing in a steering control of a rear wheel RW an influence of the second condition quantity, that is, an influence of steering control with a time delay, responsibility of a vehicle for steering the front wheel FW is slowed, but a yaw rate, roll angle and lateral acceleration are decreased when the front wheel FW is steered. Thus, a load collapse and an uncomfortable feeling of the crew can be prevented.