To provide a valve that can endure extremely high pressure with large reliability, by fixing a diaphragm to a valve housing outside it and a closure member inside it, and filling a support hollow space partitioned by this with a noncompressible and deformable support medium.

A valve 1 has a valve housing 2 which is penetrated by a through-flow channel 3 and is constituted with lower and upper formation bodies 8, 9, a closure member 13 is inserted into a guide portion 12 with a cylindrical cross section formed on the formation body 9 in the upper part of the housing. The closure member 13 is provided with a valve element 14 projecting to the lower part of a valve chamber 6, and a differential piston 15 and a valve rod 16 arranged in its upper part. The upper side of the valve chamber 6 is closed with a diaphragm ring 28, and a support hollow space 29 partitioned by this is filled with noncompressible support liquid 29. Volume of the support hollow space 29 is kept constant during vertical motion of the closure member 13, and a step 32 is formed in the differential piston 15 for keeping the volume of this support hollow space 29 constant.