A receiving housing is displaceable in the direction to be pushed out from the opening of a bottom panel by a connecting operation. One end of a lever can be engaged with a counterpart housing and the other end can be engaged with a rotating shaft protrusion of the bottom panel. The counterpart housing is pulled towards the receiving housing by means of the lever that pivots around a portion to be engaged with the rotating shaft protrusion of the bottom panel as a fulcrum by the displacement of the receiving housing in cooperation with the connecting operation.