PURPOSE: To improve the windability of a metallized plastic film and to stabilize the dielectric strength of a capacitor obtd. from the film by metallizing the inside of the curl of a plastic film and straightening the film by the resulting two-layered structure.

CONSTITUTION: A plastic film as a base curls because it is rolled. A metallic film is formed on the inside of the curl of the curled film by vapor deposition, sputtering or other method. Action by which the resulting metallized plastic film is curled with the plastic film face inward acts and the plastic film is straightened.