A DC-DC converter is mounted on a vehicle. The DC-DC converter includes: a bidirectional DC-DC converter that is connected between a capacitor for pre-charging connected to a first battery and a second battery differing from the first battery and can perform bidirectional output; and a unidirectional DC-DC converter that is connected in parallel with the bidirectional DC-DC converter and can perform output in one direction to a side of the second battery. During activation of the vehicle, the controller actuates the bidirectional DC-DC converter to start pre-charging the capacitor by using power of the second battery and starts actuating the unidirectional DC-DC converter later than initiation of the actuation of the bidirectional DC-DC converter.