PURPOSE: To improve damping effect and effectively damp at one position by detecting pressure pulsation of fluid in a piping, generating pressure pulsating wave of reverse phase in a pressure gas chamber on the lower stream, and canceling the pressure pulsation with it.

CONSTITUTION: Pulsation of fluid in a piping 1 is detected by a pulsation detecting means 11, magnitude of amplitude of the pulsation and waveform of the oscillation are computed in a computing part 12, and a control signal corresponding to time variation is outputted. It is received in a gas pressure control part 14, the pressure of reverse phase and similar waveform against the pressure pulsating wave in a diaphragm part 3 is transmitted to a pressure gas chamber 5, and the initial pressure pulsating wave is damped by canceling normal and reverse pressure pulsating wave. Even though supply of pressure gas from a pressure gas supply means 13 is stopped and the gas pressure control part 14 is not operated, because the diaphragm part 3 is deformed by pressure pulsation of fluid in the piping 1, the pressure pulsation is damped.