PURPOSE: To prevent the occurrence of pulsation, by a method wherein the low pressure side of an accumulator is connected to an accumulator driving line lead from a primary line, the high pressure side thereof is connected to a secondary line, and a delivery pressure on the high pressure side is set to a value lower than the delivery pressure of a booster.

CONSTITUTION: A booster 15 is actuated from a liquid pressure source 1 through a primary line 12, and a liquid pressure is fed to an orifice 21 through a secondary line 20. The low pressure side of an accumulator 32 is connected to an accumulator driving line 31 lead from the primary line 12. The high pressure side of the accumulator 32 is connected to a secondary line 20, and the delivery pressure on the high pressure side of the accumulator 32 is set to a value slightly lower than the delivery pressure of the booster 15. This enables direct prevention of the occurrence of pulsation of superhigh pressure water by means of an accumulator.