After turning a main relay to a full off-state and turning a charger relay to a full off-state or a half off-state only one of a positive-side switch and a negative-side switch is turned of voltage application processing is performed to control a bidirectional DC-DC converter to apply an output voltage of an accessory battery to a power cable after boosting. After the voltage application processing, check processing is performed to check whether a short-circuit is present in the charger relay by comparing a terminal voltage of a first capacitor and a terminal voltage of a second capacitor. After the check processing, discharge processing is performed to control the DC-DC converter to discharge at least the first capacitor.