PURPOSE: To obtain a steering device capable of controlling suitable steering with simple constitution and having fail-safe function.

CONSTITUTION: Tires 12 are steered with a steering wheel 14, and apart from this the tires 12 are driven with a hydraulic motor 50. Meanwhile, actual yaw rate of a vehicle is detected, and a target yaw rate is set. According to the compared result of these yaw rates, the hydraulic motor 50 is controlled to drive with a controller 32 to adjust the steering angle of the tires 12, so as to conform the actual yaw rate to the target yaw rate. Further, when an electric trouble is generated in a vehicle, a fail-safe valve to interrupt fluid flow of the hydraulic motor 50 is arranged, so as to enable to continue ordinary steering even at abnormal working.