On one side of the mold body is configured to selectively open and close an extrusion passage for the rib forming part forming a rib for rigidity reinforcement inside the pipe member integrally molded to the extrusion Guide housing is integrally fixed to the inner end face of the mold body which is disposed inside the container, the two side ends has a sliding groove is formed; In the inside of the guide housing, a sliding block disposed in correspondence with the inlet of the extrusion passage for forming ribs formed on the inner end face of said mold body; The respective one ends to the two side ends of the sliding block is fixed, the other end of each of the left and right guide bar which is provided slidably in the sliding groove on both sides of the guide housing to guide said sliding block; It is fixed to one side of the container, for the actuation rod is formed tubular member characterized in that connected to the one of the left and right guide bars at the front inner side of the container and a drive cylinder for transmitting the sliding force to the sliding block providing an extrusion die unit.