To suppress receive of an influence of temperature change, and adapt this valve to a compressor of a super critical pressure steam compression cycle by filling inert gas in a spring chamber, in a structure wherein a diaphragm is held and fixed between a valve main body part and a pressure responding part having a spring case of forming a spring chamber.

Pressure Ps is introduced from an introducing port 29 to a pressure receiving chamber 21 of a pressure regulating valve 1. When the pressure Ps from an evaporator lowers, a diaphragm 11 in the pressure receiving chamber 21 moves in a direction where an operating rod 24 is pushed down by a pressure setting spring 16 in a spring chamber 15 and pressure of inert gas filled in the spring chamber 15, and thereby, a ball valve element 25 is opened. A refrigerant introduced from the introducing port 31 is guided into a crankcase of a compressor via a supply port 30. A compression capacity of the compressor is reduced by widening a slant rotating angle of a swash plate. When pressure in the pressure receiving chamber 21 climbes up, a ball valve element 25 is closed. On the other hand, the compression capacity of the compressor is increased by reducing the slant rotating angle of the swash plate.