A method of controlling a rotary electric machine, which is configured to supply an electric control amount to a power conversion unit, which is configured to convert a DC voltage from a power source into a drive current to the rotary electric machine in accordance with the electric control amount, the method including: using a conversion map, which is used to calculate the electric control amount based on a rotation speed of the rotary electric machine at a particular DC voltage of the rotary electric machine and a required command value; and calculating the electric control amount in accordance with a ratio between the particular DC voltage and the rotation speed of the rotary electric machine in determining the electric control amount in accordance with the conversion map.