Abstract: A hydraulic exerciser formed with a structure comprising a cylinder and an oil reservoir surrounding the cylinder and communicated therewith, a piston is slidably mounted in the cylinder, the upper end of the piston rod is protruded beyond a bearing which is supported on the upper end of the cylinder and the oil reservoir and provided with oil passages. There is a controlling mechanism provided with respect to the oil passages, which comprises a disc member has a sloped outer ring portion and an inner ring portion with a spiral contour; and a bushing member associated with the disc member and on which an oil hole is provided, with the turning of the bushing member relative to the disc member, the oil hole is covered by the spiral inner ring portion with different degrees and so that the opening thereof can be adjusted, the resistance of the oil when passing the oil hole and the oil passages thus can be varied.