To inhibit the generation of particles every opening and closing operation of a valve.

In a diaphragm valve where a diaphragm 6 is pressed to a valve seat face of a valve casing 1 for cutting off the liquid flowing inside the valve casing, at least the valve casing 1 is a PFA molding, and the diaphragm comprises a central valve element 6a, a circular thin film part 6b integrally formed around the valve element, and a cylindrical holding part 6c integrally formed around the circular thin film part. Further the circular thin film part 6b is curved in such manner that a section thereof has an upward spherical shape, a root part of an inner periphery thereof is almost vertically connected to an upper face of the valve element 6a, a root part of an outer periphery thereof, is almost vertically connected to an upper edge of the inner peripheral face of the cylindrical holding part 6c, and a rubber 17 for damper is fitted to an outer periphery of a piston rod 12 of a cylinder 9 of a valve driving part for pressing the diaphragm 6 to a valve seat, to be held between the piston 11 and a cylinder case 10.