A connector includes a switch, a button configured to move a card of the switch, a spring connected to the button, and a connection terminal connected to the switch. When another connector is inserted into the connector, the connection terminal contacts a connection terminal of the other connector, and when the other connector is further inserted, the button is pressed by the other connector to move the card to close the switch to allow electric power to be supplied from the connector to the other connector, and the spring has its locking part engaging with an engaging part of the housing of the connector. When the other connector is pulled off of the connector, the spring has its locking part disengaging from the engaging part to open the switch, with the connection terminals contacting each other, to interrupt the supply of electric power.