A method of decorating a three-dimensional object, which performs a thermal transfer by causing a flat thermal transfer foil to adhere favorably to a molded article of a comparatively tall shape. Providing a planar heater (17) at the side of a support jig (5) to partially heat and extend a thermal transfer foil (71) and fixing a shape cutter (19) to the side of a molded rubber mold (3) and mounting a cutting mechanism which cuts the thermal transfer coil immediately before the molded rubber mold reaches the drop point, so that the thermal transfer foil is favorably caused to favorably adhere to the molded article (6).