It is aimed to enable a peak value reduction of connection resistance without hindering a connecting operation. A first housing includes an initial position holding portion for holding a movable housing at an initial position and a connection position holding portion for holding the movable housing at a connection position. A facing interval between the movable housing at the initial position and the second housing is narrower than that between a housing body and the second housing, and a facing interval between the movable housing at the connection position and the second housing is equal to that between the housing body and the second housing. The second housing is provided with a holding releasing portion for releasing holding by the initial position holding portion when the movable housing reaches a position just before a proper connection position in a connection process to the first housing.