Parameters relating to rotation of a motor (2) measured every constant time are acquired and the moving average of each constant interval of the parameters is calculated. The calculated moving averages are input to a training model trained so as to output a temperature of magnets attached to a rotor (7) of the motor (2) when the moving averages of the parameters relating to rotation of the motor (2) are input, and an estimated value of the magnet temperature output from the model is acquired. Next, the acquired estimated value of the magnet temperature is output.