The vehicle power supply apparatus includes: a drive power supply that supplies electric power to a motor for generating drive power; an auxiliary power supply that supplies electric power to a motor controller and door lock controllers; and a backup power supply. A control method for the vehicle power supply apparatus includes: discharging the in-vehicle equipment by using the electric power that is supplied from the backup power supply when it is determined that a vehicle has collided with an obstacle; and operating the door lock controllers by using the electric power that is supplied from the backup power supply after a lapse of a specified time period since initiation timing of the discharging step so as to unlock doors.