In a fluid control valve, a valve part houses a diaphragm in a valve body including a valve seat, first and second ports, and a drive part includes a piston dividing a piston chamber in a cylinder body into first and second chambers, and a rubber sealing member attached to the outer peripheral surface of the piston. A constriction is provided between the piston chamber and the surface of the cylinder body contacting the valve body. The cylinder body is formed with an exhaust port communicating with the first chamber, an operation port communicating with the second chamber, and a purge port communicating with a fluid non-contact chamber. The piston is formed with a flow path which enables communication between the first chamber and the fluid non-contact chamber. Accordingly, a temperature increase of the drive part can be restricted, and degradation of internal parts can be prevented.