A power supply device suitable for a vehicle, the power supply device comprising: a power storage device that is configured to be charged by receiving power from outside the vehicle; an inlet to which a charging connector is connectable; a connector connection detection circuit configured to detect whether the charging connector is connected to the inlet; a charging relay that is configured to connect the power storage device to the inlet; a power line that is connected to the power storage device via the charging relay; a first signal line that is a path through which a current flows to the connector connection detection circuit; a second signal line configured to send a charging permission command and a charging inhibition command from the vehicle to a charger outside the vehicle; a ground line configured to make a ground potential equal to a ground potential of the charger; and an electronic control unit configured to control the connector connection detection circuit and the charging relay, wherein the power line, the first signal line, the second signal line, and the ground line are configured to be connected to corresponding lines on the charger side when the charging connector is connected to the inlet, while the connector connection detection circuit is not in operation, the second signal line is configured to have a state thereof fixed in such a way that the second signal line indicates a charging inhibition command if the ground line is disconnected, and while the connector connection detection circuit is in operation, the second signal line is configured such that a charging permission command is indicated by means of a sneak current flowing in a closed circuit which is formed via the first signal line and the second signal line, when the ground line is disconnected, characterized in that the control unit is configured not to perform an operation confirmation of the connector connection detection circuit if the charging relay is in an ON state and is configured to perform the operation confirmation of the connector connection detection circuit if the charging relay is in an OFF state regardless of a content of the command sent through the second signal line, the operation confirmation being performed to confirm whether the connector connection detection circuit normally detects the connection of the charging connector, that is, the connector connection detection circuit operates correctly, so that no abnormality of the connector connection detection circuit occurs. a power storage device that is configured to be charged by receiving power from outside the vehicle; an inlet to which a charging connector is connectable; a connector connection detection circuit configured to detect whether the charging connector is connected to the inlet; a charging relay that is configured to connect the power storage device to the inlet; a power line that is connected to the power storage device via the charging relay; a first signal line that is a path through which a current flows to the connector connection detection circuit; a second signal line configured to send a charging permission command and a charging inhibition command from the vehicle to a charger outside the vehicle; a ground line configured to make a ground potential equal to a ground potential of the charger; and an electronic control unit configured to control the connector connection detection circuit and the charging relay, wherein the power line, the first signal line, the second signal line, and the ground line are configured to be connected to corresponding lines on the charger side when the charging connector is connected to the inlet, while the connector connection detection circuit is not in operation, the second signal line is configured to have a state thereof fixed in such a way that the second signal line indicates a charging inhibition command if the ground line is disconnected, and while the connector connection detection circuit is in operation, the second signal line is configured such that a charging permission command is indicated by means of a sneak current flowing in a closed circuit which is formed via the first signal line and the second signal line, when the ground line is disconnected, characterized in that the control unit is configured not to perform an operation confirmation of the connector connection detection circuit if the charging relay is in an ON state and is configured to perform the operation confirmation of the connector connection detection circuit if the charging relay is in an OFF state regardless of a content of the command sent through the second signal line, the operation confirmation being performed to confirm whether the connector connection detection circuit normally detects the connection of the charging connector, that is, the connector connection detection circuit operates correctly, so that no abnormality of the connector connection detection circuit occurs.