PURPOSE:To contrive to save energy, make the whole device compact and form high quality transmission belts in a short time by a method wherein heating ad pressurizing are done by separate means and at the same time the interior of a vulcanizing recessed part of a hot plate is heated by supplying heating medium in the hollow parts of the hot plate. CONSTITUTION:A vulcanizing recessed part 7, the front face of which is open, is formed peripherally. At the same time, drum-shaped hot plates 5 and 6, which have hollow parts 8 and 9 adjacent to the recessed part 7 and tare widthwise splitable, a heating means, which supplies heating medium to the hollow parts 8 and 9 of the hot plates in order to heat the hot plates 5 and 6, and a mold 12, the back and side surfaces of which closely are brought into contact with the interior of the vulcanizing recessed part 7, are equipped. A molding belt 2, which is arranged in the interior of the vulcanizing recessed part 7 so as to closely contact with the mold, is vulcanized by being heated with the heating means and simultaneously pressing from the opened surface of the vulcanizing recessed part 7. Since the heating medium is circulated only through the small- space hollow parts 8 and 9, the energy can be reduced by 20-70% as compared with that by vulcanizer system, resulting in contriving to save energy.