An alternator controlling method includes: performing alternator braking/driving force control such that alternator braking/driving force generated by an alternator mounted in a vehicle and applied to the vehicle is controlled based on a running state of the vehicle; calculating an SOC value based on a charge status of a battery; calculating an SOC correction value based on the alternator braking/driving force Fo; determining an accelerating/decelerating state of the vehicle; setting a target voltage based on the accelerating/decelerating state and the SOC correction value; and performing battery charging control by causing the alternator to generate electrical power based on the target voltage. This enables efficient recovery of energy produced during electrical power generation by the alternator, taking account of the alternator braking/driving force control.