A first housing includes a wide connection surface and a bearing formed on an edge on one side along the longitudinal direction of the connection surface. A second housing includes a side surface formed to face in a direction intersecting a connecting direction of the first and second housings. A lid is displaceable about a shaft supported by the bearing portion to a closed position where the lid covers the connection surface and an open position where the lid member contacts the side surface. The lid is biased from the open position to the closed position by a biasing member. An outer shape of the lid has a long side arranged along the longitudinal direction of the connection surface and a short side intersecting the long side and shorter than the long side.