To reduce pulsation even if the frequency of the pulsation varies by adjusting the air column of a gas sealed part.

A branch pipe 2 is fitted atop of a liquid transport pipe 1 and gas is charged in it. The branch pipe 2 is provided with a pressure container 3 in which high-pressure gas is charged through a 1st solenoid valve 4, a 2nd solenoid valve 5 which releases the gas in the branch pipe 2 to the atmosphere, and a distance sensor 7, and the transport pipe 1 is provided with a pressure sensor 6; and the signals of the sensors 6 and 7 are inputted to a controller 8 which controls the solenoid valves 4 and 5. The controller 8 determines a target value of a resonance frequency according to the signals of the sensors 6 and 7, calculates the air cylinder length of the branch pipe 1 which matches the resonance frequency to the target value, and controls and opens or closes the solenoid valves 4 and 5. Therefore, even when the pulsation frequency varies, that is followed up and the pulsation is reduced.