Seal portions at two locations communicate with each other and are integrated with each other to realize a waterproof structure. A first seal portion is provided onto an outer surface at a tip of a central cylinder inside a housing main body to realize a waterproof structure where a gap between the outer surface and a housing of a mating electrical connector is sealed in a waterproof manner. The seal portion is also connected to an inner surface of the central cylinder through a communication hole provided in the central cylinder, and a second seal portion is provided on the inner surface, integrally with the seal portion, to realize a waterproof structure where a gap between the inner surface and a terminal holder is sealed in a waterproof manner.