PURPOSE: To manufacture the large amount of a sewage disposal thak of high strangth at a low cost, by shaping the press-bonded parts at both ends of a vinylchloride resin pipe at the time of blow molding, also shaping the flow-in pipe part and the flow-out pipe part of the sewage simultaneously along its line.

CONSTITUTION: A vinylchloride resin pipe 17 is blow molded between an upper mold 12 and a lower mold 13. The clamps 14, 14, 14', 14' are attached to both right and left ends of the upper and lower molds 12, 13, while the concave parts 22, 22' which are fitted to the inner molds 15, 15' are shaped at their end faces. Both ends of the vinylchloride resin pipe 17 are bent inside respectively by the clamps and the press-bonded parts 20 are shaped, at the same time a flow-in pipe part 9 and a flow-out pipe part 10 are press-bonded and shaped. Blow molding is preformed by blowing a compressed air into the vinylchloride resin pipe 17 from a compressed air introducing pipe 21 provided at the inner mold 15.