A temperature detection condition of a temperature detection unit used in a motor system is determined by: obtaining a phase current value flowing through a motor device and obtaining a temperature detection value; calculating, as an integrated phase current value, at least one of a first integrated phase current value, which is obtained by integrating an amount by which the phase current value exceeds a first phase current threshold, and a second integrated phase current value, which is obtained by integrating an amount by which the phase current value is smaller than a second phase current threshold that is equal to or smaller than the first phase current threshold; and determining an amount of variation in the temperature detection value detected by the temperature detection unit following the start of determination of the temperature detection condition and an amount of variation in the calculated integrated phase current value.