PURPOSE: To improve stability of steering at a high speed, in a power steering device of rotary valve type, by resisting rotation from a spring through a device, providing the device between an input shaft and worm shaft and applying back pressure in a recirculation oil passage to said device.

CONSTITUTION: An axially directional hole 34 and a through hole 35, communicated to said hole 34 and extended at a right angle with the axial direction, are provided in the point end side of an input shaft 24. One head part of a torsion bar 36 is fitted and coupled by a pin to the axially directional hole 34, and steel balls 38 are in-out movably fitted to the through hole 35 by interposing a coil spring 37. The steel balls 38 are forcibly contacted to V-shaped recessed parts 39 provided in the internal peripheral surface of a worm shaft 19. The steel ball 38 is arranged to receive back pressure in a recirculation flow circuit, if the back pressure in the recirculation flow circuit is increased, the steel ball 38 is pressed into the through hole 35 against the spring 37, in this way, an input characteristic can be changed.