TWI770691B

The invention provides a diagnostic device including: an input/output unit that receives an input of a current value indicating a value of a current of an electric motor measured by a sensor; a frequency analysis unit that converts the current value measured by the sensor into a frequency intensity; a deterioration mode decomposition unit that uses a state mode model indicating a change situation of a frequency intensity in a part constituting the electric motor to calculate an activity level indicating a time series change of a deterioration intensity for each state mode model from the frequency intensity; and an abnormality determination unit that determines a deterioration and an abnormality of each part using the activity level.