To allow a feedback chamber to communicate with a pressure gauge by using a communication path between a feedback member and a pressure gauge guide without using any conduction hole in a valve body wall or bonnet wall.

A pressure gauge guide 71 is connected with a pressure gauge 93, and a through-hole 56 communicating with a feedback chamber 47 is formed at a feedback member 42, and the through-hole 56 is allowed to communicate through through-pipe lines 62 and 64 with the pressure gauge guide 71. A pressure adjusting nut 39 is supported by the bonnet 33 so as to be freely rotatable, and a pressure adjusting spring bearing 40 is supported by the bonnet 33 so as to be freely movable in the axial direction but not turnable. The pressure adjusting nut 39 is rotated according to the rotation of a handle 78, and the pressure adjusting spring bearing 40 is moved to the axial direction.