A seal ring (80) is fit on an outer surface of a housing main body (11) and rests on a resting portion. When a receptacle (62) is fit externally on the housing main body (11), outer peripheral lips (84) of the seal ring (80) closely contact an inner surface of the receptacle (62). The seal ring (80) includes front and rear rings (86, 87) extending in a front-back direction at opposite front and rear sides of the outer peripheral lips (84). The rear ring (87) is longer in the front-back direction than the front ring (86). A first housing (10) includes a protrusion (23) for radially sandwiching the rear ring (87) between the protrusion (23) and the housing main body (11). When the receptacle (62) is fit externally on the housing main body (11), the protrusion (23) is covered with an opening portion (66) of the receptacle (62).