PURPOSE: To prevent the remaining of undesirable marks based on the fold of a cylindrical shrinkable film having a fold even when an article is covered by using said film, by shrinking the shrinkable film while keeping the film so as to make the pressure applied to the surface of the film in the side of the article larger than that applied to the other surface side of said film.

CONSTITUTION: The pressure Pin applied to the surface of a shrinkable film in the side of an article and the pressure Pout applied to the other surface side of said shrinkable film are kept so as to form the relation of Pout<Pin to shrink said film. That is, the base body and auxiliary cylinders 2W10 covered with the shrinkable film 12 are downwardly moved and an air supply pipe 20 is fitted to the opening 10a of the lower auxiliary cylinder 10 and, at this point of time, compressed air is supplied in the film 12 from a compressed air source 18 through an air supply pipe 20. Thereafter, the cylinders 2W10 are further downwardly moved to immerse the whole in hot water 16. The shrinkable film is shrunk by heating due to hot water in such a state that the pressure of compressed air is kept larger than water pressure of hot water 16.