An electric load medium works at a generation voltage of a generator while at least one processor is controlling the generation voltage of the generator considering a traveling state of a vehicle. The generation voltage of the generator is controlled considering the traveling state of the vehicle, when a first condition that a value that indicates a state of charge of a battery of the vehicle that is charged by power generated by the generator is less than or equal to the predetermined threshold is satisfied, and a second condition that the vehicle is during deceleration is satisfied. Otherwise, the generation voltage of the generator is controlled considering working of the electric load medium.