A hydraulic machine comprising: a rotor shaft; a cylinder; a piston forming a working chamber together with the cylinder; a high-pressure valve and a low-pressure valve provided for the working chamber, wherein the hydraulic machine is configured to perform conversion between rotational motion of the rotor shaft and reciprocal motion of the piston, and wherein at least one of the high-pressure valve or the low-pressure valve comprises a solenoid valve which includes: a valve body configured to be attracted toward a core by a magnetic force generated by supplying electric current to a coil; and a position restricting part for restricting a position at which the valve body is closest to the core when attracted, wherein the position restricting part comprises a non-magnetic layer disposed between the valve body and the core; and a diagnosis system comprising: a pressure sensor for detecting a pressure of the working chamber; a response-delay calculating part configured to calculate, on the basis of a temporal change in a cylinder pressure obtained by the pressure sensor, a response delay which is a period of time from a point of time (t 1) when supply of electric current to the coil is stopped to a point of time (t 2) when the working chamber pressure begins to decrease; and a damage detecting part configured to detect a damage of the solenoid valve, such as a damage of the position restricting part on the basis of the response delay. a rotor shaft; a cylinder; a piston forming a working chamber together with the cylinder; a high-pressure valve and a low-pressure valve provided for the working chamber, wherein the hydraulic machine is configured to perform conversion between rotational motion of the rotor shaft and reciprocal motion of the piston, and wherein at least one of the high-pressure valve or the low-pressure valve comprises a solenoid valve which includes: a valve body configured to be attracted toward a core by a magnetic force generated by supplying electric current to a coil; and a position restricting part for restricting a position at which the valve body is closest to the core when attracted, wherein the position restricting part comprises a non-magnetic layer disposed between the valve body and the core; and a valve body configured to be attracted toward a core by a magnetic force generated by supplying electric current to a coil; and a position restricting part for restricting a position at which the valve body is closest to the core when attracted, wherein the position restricting part comprises a non-magnetic layer disposed between the valve body and the core; and a diagnosis system comprising: a pressure sensor for detecting a pressure of the working chamber; a response-delay calculating part configured to calculate, on the basis of a temporal change in a cylinder pressure obtained by the pressure sensor, a response delay which is a period of time from a point of time (t 1) when supply of electric current to the coil is stopped to a point of time (t 2) when the working chamber pressure begins to decrease; and a damage detecting part configured to detect a damage of the solenoid valve, such as a damage of the position restricting part on the basis of the response delay. a pressure sensor for detecting a pressure of the working chamber; a response-delay calculating part configured to calculate, on the basis of a temporal change in a cylinder pressure obtained by the pressure sensor, a response delay which is a period of time from a point of time (t 1) when supply of electric current to the coil is stopped to a point of time (t 2) when the working chamber pressure begins to decrease; and a damage detecting part configured to detect a damage of the solenoid valve, such as a damage of the position restricting part on the basis of the response delay.