PURPOSE: To strengthen the connecting part of two parts when dipping in a paste sol liquid tank the metal moulds of an air bag part shape and a pipe part shape preheated in a furnace by dipping the pipe shape metal mould for a longer time than the air bag shape metal mould.

CONSTITUTION: After applying a mould parting agent all over the surface of a metal 1 previously, the metal mould is preheated, and when dipping it in a paste sol liquid tank, a pipe shape metal mould part 2 is dipped for a time about 3W5 times the dipping time of an air bag shape metal mould part 3. Next, they are heated in an electric furnace to make the paste sol collected on the surface of the metal mould 1 gel, then cooled, and a formed article 11 consisting of an air bag part 13 and pipes 12 is separated from the metal mould 1.