A first analyzing step is a step that conducts numerical analysis of a flow field but does not conduct numerical analysis of a temperature field in a state in which a motor rotor is rotating. The second analyzing step is a step that conducts numerical analysis of both the flow field and the temperature field after the first analyzing step ends. Accordingly, before numerical analysis of the flow field and numerical analysis of the temperature field are conducted together, numerical analysis is conducted first on the flow field in first analyzing step before it is conducted on the temperature field. As a result, compared with when the second analyzing step is executed from the beginning without conducting the first analyzing step, the calculation load of the numerical analysis on an electronic calculator can be reduced, which enables the time that it takes to conduct the numerical analysis to be shortened.