A dummy pin includes a pin main body that is to be inserted into the at least one terminal insertion port and is formed by molding resin, the pin main body having: a waterproof portion having a cylindrical seal surface that makes tight contact with an inner surface of the at least one seal hole by elastically compressing a part of the two or more lip portions of the waterproof member; and a falling-off prevention portion having one or more concave portions that are partially recessed from the seal surface toward the central axis and that a remaining lip portion of the two or more lip portions of the waterproof member enters, the seal surface forming a continuous surface over an entire circumferential direction of the waterproof portion.