PURPOSE: To save electric energy by a method wherein a switch is provided to detect that a fluid pressure is needed to assist steering according to a steering input, and a pump motor is driven and controlled by an output therefrom.

CONSTITUTION: Wheels are steered through movement in the axial direction of a rack bar 2 through a rack and pinion gear 1 by steering input torque through a steering column 3. Further, in this case, a steering assist force is applied on the rack bar 2 by the power of a hydraulic servo motor 4, and working liquid from a pump 5 driven by a motor 6 is fed to and discharged through control valve 8. In this steering device, a switch 14 is provided to interlock with relative movement between two elements 18 during steering input. When a contact 17 is opened by this switch 14, a relay 9 is stopped and a contact 10 is brought into a closed state 10a so as to drive the motor 6.