PURPOSE: To constitute the power steering device compactly, and to adjust the reaction force of a ring spring easily by using the ring spring for the spring reaction force device while the reaction force of the ring spring is adjusted by means of a preset pin with an eccentric shaft.

CONSTITUTION: A screw hole 10 penetrating in the radial direction of a valve body 2 is formed to the valve body, and the preset pin 12, an eccentric section 11 thereof projects to an inside diameter of the valve body 2, is screwed into the screw hole. A load pin 13 projeting opposing to the eccentric section 11 of the pin 12 is studded to an outside diameter of an input shaft 6, and the ring spring 15 with opening end sections 15a, 15b simultaneuosly holding the eccentric section 11 and the load pin 13 from the circumferential direction of the input shaft is wound on the input shaft 6. A position of the eccentric section 11 is adjusted by turning the preset pin, thus regulating the reaction force of the ring spring.