PURPOSE: To prevent the insulation breakage due to the concentration of an electric field without causing damage to an insulating sheet by winding a metallic sheet and an insulating sheet on an iron core with overlapping and displacing the metallic sheet upward and downward by each winding.

CONSTITUTION: A metallic sheet 1 and an insulating sheet 2 are wound on an iron core with overlapping for winding of a foil-wound transformer. At this time, the sheet 1 is wound with being displaced 0.5W5.0mm upward and downward by each winding. Thus, the damage of the insulating sheet due to the metallic sheet is prevented and the electric-field concentration onto the ends of the sheets is alleviated to obtain the foil-wound transformer of high insulation strength and mechanical strength.