To configure a mechanism for regulating a pressure to a constant outlet pressure with high accuracy especially in a wide range of an inlet pressure, with a small and simple structure, in regulating the pressure such that the constant outlet pressure is obtained regardless of fluctuation of the inlet pressure of a high pressure gas.

This pressure regulator has: a first stage governor mechanism 2 having a first pressure regulating valve 21 decompressing the inlet pressure by an introduction gas to an intermediate pressure; and a second stage governor mechanism 3 having a second pressure regulating valve 31 decompressing the intermediate pressure to the outlet pressure. The first stage governor mechanism 2 and the second stage governor mechanism 3 are disposed such that an excursion direction of a first diaphragm 22 operating the first pressure regulating valve 21 in the first stage governor mechanism 2 and an excursion direction of a second diaphragm 32 operating the second pressure regulating valve 31 in the second stage governor mechanism 3 cross. In each of the first and second pressure regulating valves 21, 22, one of a valve element and a valve seat includes an elastic body, and a swelling deformation direction of the elastic body is set to a direction different from a valve opening/closing operation direction to allow application even to dimethyl ether.