A hydraulic machine comprising: a rotation shaft; a cam configured to rotate with the rotation shaft; a cylinder disposed radially inside or outside the rotation shaft; a piston configured to be reciprocable in the cylinder along a radial direction of the rotation shaft in conjunction with rotational motion of the cam; a connecting rod including a first end portion connected swingably to the piston and a second end portion disposed opposite to the first end portion; a hydrostatic pad disposed on the second end portion of the connecting rod, the hydrostatic pad including a sliding surface facing an outer surface of the cam; and a lubricant-fluid supply channel disposed on the hydrostatic pad, for supplying a lubricant fluid to the sliding surface of the hydrostatic pad, wherein the hydraulic machine is configured so that a pressure in a working chamber formed by the piston and the cylinder changes cyclically and alternately between a first pressure P 1 and a second pressure P 2 larger than the first pressure P 1, in accordance with the reciprocating motion of the piston, and wherein the hydrostatic pad is configured to retain a liquid film of the lubricant fluid between the sliding surface and the outer surface of the cam, characterized in that the hydrostatic pad is configured to retain the liquid film of the lubricant fluid having a thickness of d or more between the sliding surface and the outer surface of the cam at least when the pressure in the working chamber is the second pressure P 2, wherein d is determined to correspond to an amount of deformation of the hydrostatic pad at the time when the pressure in the working chamber is the second pressure P 2. a rotation shaft; a cam configured to rotate with the rotation shaft; a cylinder disposed radially inside or outside the rotation shaft; a piston configured to be reciprocable in the cylinder along a radial direction of the rotation shaft in conjunction with rotational motion of the cam; a connecting rod including a first end portion connected swingably to the piston and a second end portion disposed opposite to the first end portion; a hydrostatic pad disposed on the second end portion of the connecting rod, the hydrostatic pad including a sliding surface facing an outer surface of the cam; and a lubricant-fluid supply channel disposed on the hydrostatic pad, for supplying a lubricant fluid to the sliding surface of the hydrostatic pad, wherein the hydraulic machine is configured so that a pressure in a working chamber formed by the piston and the cylinder changes cyclically and alternately between a first pressure P 1 and a second pressure P 2 larger than the first pressure P 1, in accordance with the reciprocating motion of the piston, and wherein the hydrostatic pad is configured to retain a liquid film of the lubricant fluid between the sliding surface and the outer surface of the cam, characterized in that the hydrostatic pad is configured to retain the liquid film of the lubricant fluid having a thickness of d or more between the sliding surface and the outer surface of the cam at least when the pressure in the working chamber is the second pressure P 2, wherein d is determined to correspond to an amount of deformation of the hydrostatic pad at the time when the pressure in the working chamber is the second pressure P 2.