PURPOSE: To reduce the cost of equipments, rationalize by reduce manhours, facilitate the management of process and improve an yield as well as the strength of fusion bonding, by a method wherein a heat generating body is supported so as to be interposed between respective materials to be bonded by fusion, and the heat generating body is conducted to fuse said materials and press bond them.

CONSTITUTION: A heat generating body 3 is a gasket type formed sheet which is formed by mixing and blending a resin of substantially the same quality as vessels 1, 2 with proper amount of metallic short fibers 3a. The heat generating body 3 is a flat sheet provided along the fusion-bonding surface of the vessels and is connected to electrodes 3b. When a pressure P is applied at the time of fusing the fusion-bonding surfaces of the vessels 1, 2, the vessels can be bonded by fusion perfectly. An insulating distance S2, provided between the electrodes 3b, may be bored additionally to apply a plug or the hole may be utilized as the penetrating hole of a heater. Thus the amount of electric conduction and a time corresponding to the value of the material resistance of the heat generating body are simply selected and the heat generating body is pressed for a proper time, therefore, a complicated setting of various process conditions in a hot-air fusion bonding process may be eliminated.