PURPOSE: To improve dielectric stength of the cut surface of a capacitor and prevent its insulation resistance from deterioration, by using a specific lubricant when the layer-built capacitor is cut.

CONSTITUTION: At cutting work of a capacitor, in which the dielectric is a lacquer thin film, polybutene is used as a lubricant and intruded into the lacquer thin films to prevent deterioration of an insulation resistance value in a cut surface.