In a connector, a tapered portion is formed at a corner portion between a housing and a flange portion so as to be formed in parallel to a chamfered portion formed on an edge of a mounting hole in a casing. An annular seal member of the connector is mounted on an outer peripheral surface of the housing at a front side of the flange portion in an insertion direction of the housing, and is brought into close contact with an outer peripheral surface of the housing and an inner peripheral surface of the mounting hole so as to seal therebetween. A lip portion abutting on the flange portion is provided on a rear side of the seal member in the insertion direction. An outer peripheral surface and an inner peripheral surface of the lip portion are formed in parallel to the tapered portion.