PURPOSE: To prevent the lowering of capacity based on the deformation of the end part of a hose, in the injection molding of the connection part of a hose main body obtained by blow molding set to an injection mold with a partener member, by imparting a good shape to the bonded part of the hose main body and the connection part.

CONSTITUTION: At the time of injection molding, an injection material is injected in a cylindrical molding cavity 12 having a shape corresponding to that of a connection part from the injection gate 20 provided to the outer peripheral surface of said cavity in the direction right-angled to the axis of the cavity and the position of the injection gate 20 is determined so that the material injected in the molding cavity enters the space 18 for molding the overlap part of the connection part in the molding cavity 12 at the initial stage of injection.