PURPOSE: To maintain the handling performance of an apparatus always optimum by using an oil pressure as a means for energizing a rack to the pinion side and taking-out said oil pressure from the valve mechanism in the apparatus.

CONSTITUTION: The oil pressure which is supplied from an oil pressure source 9 to a valve mechanism 5 is introduced into an oil pressure chamber 7 in parallel. Accordingly, when power action is not performed in the valve mechanism 5, the oil pressure in the oil pressure source 9 flows into a drain 10, a little throttled, so the energizing force of a rack 3 in the inoperativeness of power is low, and friction decreases, and steering handling performance in improved. When power action is performed, accompanied by the increase of the road resistance, the oil pressure source 9 is allowed to communicate to a cylinder 6 by the valve mechanism 5, and the oil pressure which is introduced into the oil pressure chamber 17 increased. Accordingly, the energizing force of the rack 3 increases, and the backlash between the rack 3 and the pinion 2 becomes zero, and the strength of teeth of the both increases.