A lubricant deterioration sensor that can determine a deterioration degree of lubricant without using an external device is provided. The lubricant deterioration sensor includes an oil entering gap in which lubricant to be detected enters, a LED (21) that emits detection light to the oil entering gap, a color sensor (22) that obtains a detection value representing color information of the detection light traveled through the lubricant, a calibration unit that calibrates a measurement range of the detection value in accordance with the lubricant, a determination unit that determines a deterioration degree of the lubricant based on the detection value, and a housing in which the oil entering gap, the LED (21), the color element (22), the calibration unit, and the determination unit are disposed.