Abstract: An apparatus for processing a high-pressure liquid material has a high-pressure vessel, a pressurizing assembly for supplying a liquid material to the high-pressure vessel in order to allow the high-pressure vessel to process the liquid material under a high pressure therein, a depressurizing assembly for receiving and depressurizing the processed liquid material supplied under a high pressure from the high-pressure vessel, and a working fluid control system for controlling the depressurizing assembly. The depressurizing assembly has a plurality of cylinder device comprising respective pairs of interlinked pistons which define, in the cylinder devices, respective processing pressure chambers for selectively receiving the liquid material from the high-pressure vessel, and respective working pressure chambers for selectively receiving a working fluid from the working fluid control system.