A pressure regulator includes a housing having an inlet port through which pressurized fluid at a primary pressure is supplied, and a discharge port through which pressurized fluid at a secondary pressure lower than the primary pressure is discharged, and at the same time having a flow passage formed therein to extend from the inlet port to the discharge port, and a pressure control mechanism which is disposed on the flow passage to reduce the primary pressure to the secondary pressure. The pressure control mechanism includes a movable body including a diaphragm which is displaced in response to change in the pressure of the fluid and the movable body is provided with an abutment portion which is brought into abutment against a part of the housing to prevent the movable body from being excessively displaced when the primary pressure becomes excessively high.