A method of manufacturing a waterproof connector housing, that enables the formation of a uniform packing ring which is an integral part of the housing by engaging a hollow body of a housing with a trapezoidal engaging portion provided on a male mold, holding the housing by contacting tightly an inner wall of the hollow body with the trapezoidal engaging portion to align the center of the male mold with that of the housing, and injecting a rubber material into a packing ring forming space uniformly defined by one of both of the male and female mold through a rubber supply paths of the housing. The housing having the hollow body with tapered shoulder, a male mold having the trapezoidal engaging portion and a female mold beveled or thinned at the open edge are employed for implementing the method.