PURPOSE: To raise the back pressure of a passage ever so high as well as to aim at absorbing the fluidal noise, by installing a groove, interconnecting through the hole of a valve shaft, in a valve body, while making the valve so as to throttle a drain passage by means of a relative rotation between the body and the shaft.

CONSTITUTION: When a steering wheel is situated in neutral, a pressure fluid flowing in from the inlet port of a valve housing 1 is all refluent from an outlet port 15 via a drain passage 9 as shown in an arrow (a). At this time, a groove 16 in a valve body 3 is interconnected to a hole 11 in a valve shaft 2, and a sectional area of the drain passage 9 is large enough. Next, steering takes place, and when a torsion bar 6 is twisted and therefore a relative rotation occurs between the shaft 2 and the body 3, a power cylinder is energized to operate and thereby the pressure fluid running from one side of its fluid chamber is discharged out of the outlet port 15 by passing through the drain passage 9 as shown in the arrow (a). At this time, the positions of both the groove 16 and the hole 11 aforesaid are dislocated to some extent and thereby the sectional area of the drain passage 9 decreases so that back pressure of the passage 9 is increased instead.