To perform work with high pressure to correspond to an increase in external force during the operation with low pressure fluid.

A cylinder 2 into which a piston 1 integrally formed with a rod 15 which closes a part of a passage 13 and closes a passage 12 during its operation, is fitted, is provided with the first chamber 7 and the second chamber 9. A operating pipe line 6 is passed through the first chamber 7 and the passages 12, 13 through a valve mechanism block 5 to pass the third chamber 11 connected to an external load. A return pipe line 8 is connected to a cylinder chamber 20 and the second chamber 9 of the valve mechanism block 5. With the valve mechanism block 5, when the pipe lines 6, 8 are respectively pressurized above the determined pressures, the operating pipe line 6 is adapted to be connected to the first chamber 7. Before the valve mechanism block 5 is operated, the work is performed with the oil pressure supplied, and when the valve mechanism block 5 is operated, the piston rod 15 is projected into the third chamber 11 for the work to be performed by high pressure. Thus, by incorporating this device, a low pressure hydraulic equipment becomes cheap, and easily becomes a high pressure hydraulic equipment capable of outputting high pressure when necessary.