To provide a method and a device for manufacturing clean gas with high pressure for creating gas at high pressure, not mixed with foreign matters such as oil, such as air, oxygen gas, hydrogen gas, carbon dioxide gas, nitride gas, and helium gas by a simple system.

One end of a pressure intensifying rod of a pressure intensifying piston rod 11 integrally forming a pressure intensifying piston 11a and a pressure intensifying rod 11b is positioned to a piston 42 constituting a cylinder so as to form a space part 40Az, so that a pressure intensifier 10A is arranged at a top of a cylinder 40A constituting a compressor 50A creating compressed air with low pressure in a manner not to be influenced by lubricating oil dispersed at a bottom of a piston. A flow-in piping 101 connecting a check valve 22 for preventing reverse flow, and a flow-out piping 102 connecting a check valve 23 are arranged to a pressure intensifying chamber 10Az formed by the pressure intensifier 10A.