A charging control unit 10 includes plug contacts 161, 162 and jack contacts 181, 182 for detecting connection of a charging plug 16 of a charger 12 to a receptacle 18, a current sensor 22 for detecting completion of charging from the charger 12 to a main battery 20, a main controller 26 for starting operation of a DC-to-DC converter 24 when connection of the charging plug 16 is detected by the plug contacts 161, 162 and the jack contacts 181, 182 and for terminating operation of the DC-to-DC converter 24 when completion of charging is detected by the current sensor 22, and a distribution circuit whereby operation of the DC-to-DC converter after completion of charging is finished.