An automobile comprising: an automobile body; a door attached to the automobile body and including a door lock and a door-lock-releasing part; a battery installed in the automobile body; a backup power source device connected to the battery and disposed in an interior of the automobile body, the backup power source device including: a capacitor; a charging circuit provided in a charging path of the capacitor and performing step-down operation; a boost circuit provided in an output path of the capacitor; and a door-lock-releasing output terminal connected to the boost circuit; a vehicle electronic control unit for starting the boost circuit of the backup power source device and driving the door-lock-releasing part, using an output of the boost circuit; characterized in that, the automobile further comprises; an ignition switch connected between the battery and a side of an input end of the charging circuit of the backup power source device; a first diode connected between the input end of the charging circuit and an output end of the boost circuit; a second diode connected between the vehicle ECU and a node of the battery and the ignition switch; and a third diode connected between the vehicle ECU and the output end of the boost circuit, wherein a side of a cathode of the first diode is connected to a side of the output end of the boost circuit, and a side of an anode of the first diode is connected to the input end of the charging circuit, a side of a cathode of the second diode is connected to the vehicle ECU, and a side of an anode of the second diode is connected to a side of the node of the battery and the ignition switch, and a side of a cathode of the third diode is connected to the vehicle ECU, and a side of an anode of the third diode is connected to the output end of the boost circuit. an automobile body; a door attached to the automobile body and including a door lock and a door-lock-releasing part; a battery installed in the automobile body; a backup power source device connected to the battery and disposed in an interior of the automobile body, the backup power source device including: a capacitor; a charging circuit provided in a charging path of the capacitor and performing step-down operation; a boost circuit provided in an output path of the capacitor; and a door-lock-releasing output terminal connected to the boost circuit; a capacitor; a charging circuit provided in a charging path of the capacitor and performing step-down operation; a boost circuit provided in an output path of the capacitor; and a door-lock-releasing output terminal connected to the boost circuit; a vehicle electronic control unit for starting the boost circuit of the backup power source device and driving the door-lock-releasing part, using an output of the boost circuit; characterized in that, the automobile further comprises; an ignition switch connected between the battery and a side of an input end of the charging circuit of the backup power source device; a first diode connected between the input end of the charging circuit and an output end of the boost circuit; a second diode connected between the vehicle ECU and a node of the battery and the ignition switch; and a third diode connected between the vehicle ECU and the output end of the boost circuit,