A connecting device is provided that includes a movable part contacting an external contact terminal, and an elastic part connected to the movable part and configured to provide an elastic force enabling movement of the movable part. The connecting device also includes a support connected to the elastic part, and at least one protecting wall connected to the support and configured to protect the movable part from external forces. The connecting device further includes an extension extending from the at least one protecting wall in a direction along which the movable part moves and configured to bring the movable part close to the external contact terminal, and a base part provided within the extension and configured to reinforce the support.