MANUFACTURING METHOD OF BATTERY CASE

A manufacturing method of a battery case having a rectangular transverse cross-section in which an intermediate product having an elliptical transverse cross-section is shaped into a final product having a rectangular transverse cross-section by drawing and ironing the intermediate product multiple times to reduce a curvature radius of each corner and thicknesses of side walls formed on both sides of the corner. A difference between an ironing rate of the side wall formed on one side of the corner and an ironing rate of the side wall formed on the other side of the corner is reduced less than a predetermined difference, after the curvature radius of the corner between the side walls has been reduced shorter than a predetermined radius during the process of shaping the intermediate product into the final product.