To inflate an air bag as designed after being smoothly cleft along a tear line in time of air bag inflation by providing a decorated surface, being made up by means of a forming-simultaneous transfer method, on the whole surface or part of an air bag cover body.

When a drawing pattern layer 11 is installed on a base film 12 by means of printing and positioning for a transferring film is carried out, this transferring film is continuously supplied toward downward from the upward into an interval between a cavity type 8 and an intermediate plate 9 by a film feeder and a film winding device at the lower part, thereby determining a drawing patter position by a positioning detector. In time of taking out molding, the drawing pattern layer 11 is transferred on top of a molding 2 (air bag cover body), and the base film 12 is wound up in the lower part. The drawing pattern layer 11 of a decorated surface to be formed on a surface of the air bag cover body by means of a forming-simultaneous transferring method like this is an ink layer to be printed on the base film 12, so that it is remarkably thinner as compared with that of the conventional cover body and, further, its cleavage resistance is by for reducible.