PURPOSE: To obtain exact handle steering power in sharp turning of a steering handle at high speed running by a structure wherein the attractive force of a solenoid to the valve to control the feeding of oil to a power cylinder is controlled with a movable spool, which is shifted by the predetermined delivery pressure of a pump.

CONSTITUTION: A port 20a connected to a pump and a port 20b connected to a tank are formed in the valve main body 21. A control spool 27, by which the ports 20a and 20b are communicated to and cut-off from each other, is slidably fitted within an inner bore 23 and at the same time energized downward by means of a spring 33. The control spool 27 is put into actuation by being attracted by the solenoid 29, the exciting current of which is controlled in proportion to car speed. Furthermore, a movable spool 35 is slidably insertedly fitted in the inner bore 23 above the spool 27 and at the same time energized downward at all times by means of a spring 37 so as to abut against a stopper ring 36. The delivery pressure of the pump is applied on the undersurface of the movable spool 35. When said delivery pressure exceeds the predetermined pressure, the movable spool 35 is displaced upward, resulting in acting to weaken the attractive force of the solenoid 29.