A housing includes a housing main body provided with a terminal holding portion including a terminal accommodating chamber configured to accommodate a terminal, a retainer assembled to the terminal holding portion of the housing main body, and an annular seal member mounted to a tubular seal mounting portion formed on an assembly side to the retainer in the housing main body. The retainer includes an engaging piece protruding in a direction of assembling to the housing main body. The engaging piece is inserted into an inner side of the seal mounting portion and abuts on an inner surface of the seal mounting portion.