A hydraulic machine, comprising: a rotor shaft; a cylinder provided along a radial direction of the rotor shaft; a piston forming a hydraulic chamber together with the cylinder, the piston being configured to be guided by the cylinder so as to be reciprocally movable along the radial direction in the cylinder, and the hydraulic chamber including a central axis; a cam disposed in a cam chamber which is located on an inner side in the radial direction with respect to the cylinder, the cam being configured to rotate together with the rotor shaft in conjunction with a reciprocating motion of the piston; a low pressure hydraulic line and a high pressure hydraulic line which are respectively communicable with the hydraulic chamber and an external high/low pressure pipe (11,13); a low pressure valve disposed between the cylinder and the low pressure hydraulic line for switching a communication state between the hydraulic chamber and the low pressure hydraulic line; and a high pressure valve disposed between the cylinder and the high pressure hydraulic line for switching a communication state between the hydraulic chamber and the high pressure hydraulic line, characterized in that the low pressure hydraulic line includes the cam chamber, the hydraulic machine further comprises a low pressure passage having a first end opening to the cam chamber and a second end located on a side of the low pressure valve, and the first end of the low pressure passage is located at a radial position between a radial position of the second end of the low pressure passage and a radial position of a center of the rotor shaft. a rotor shaft; a cylinder provided along a radial direction of the rotor shaft; a piston forming a hydraulic chamber together with the cylinder, the piston being configured to be guided by the cylinder so as to be reciprocally movable along the radial direction in the cylinder, and the hydraulic chamber including a central axis; a cam disposed in a cam chamber which is located on an inner side in the radial direction with respect to the cylinder, the cam being configured to rotate together with the rotor shaft in conjunction with a reciprocating motion of the piston; a low pressure hydraulic line and a high pressure hydraulic line which are respectively communicable with the hydraulic chamber and an external high/low pressure pipe (11,13); a low pressure valve disposed between the cylinder and the low pressure hydraulic line for switching a communication state between the hydraulic chamber and the low pressure hydraulic line; and a high pressure valve disposed between the cylinder and the high pressure hydraulic line for switching a communication state between the hydraulic chamber and the high pressure hydraulic line, characterized in that the low pressure hydraulic line includes the cam chamber, the hydraulic machine further comprises a low pressure passage having a first end opening to the cam chamber and a second end located on a side of the low pressure valve, and the first end of the low pressure passage is located at a radial position between a radial position of the second end of the low pressure passage and a radial position of a center of the rotor shaft.