Oil deterioration diagnosis device

An oil deterioration diagnosis device for an operating machine, the operating machine including an oil hydraulic circuit, the oil deterioration diagnosis device comprising:

• a measurement unit configured to irradiate oil flowing through the oil hydraulic circuit with measuring light during operation of the operating machine and receive transmitted light penetrating the oil to measure continuously or intermittently absorbance or transmittance;
• and
• a diagnosis unit configured to detect changes over time in a peroxide production state wherein a peroxide contained in the oil exponentially increases resulting in an increase of the absorbance or a decrease in the transmittance of the measuring light, and configured to estimate a time for an oil change as a function indicating a relationship between a usage time of the oil and an increase of a peroxide contained in the oil,
• wherein a wave number or a wavelength of the measuring light is set at a value indicating characteristic infrared absorption corresponding to the increase in the absorbance or the decrease in the transmittance, when the oil is oxidized to consume the peroxide.