PURPOSE:To facilitate the insertion of a plate group and to prevent a drop in the capacity and internal short circuit of a battery by forming the body cross section of a cylindrical metal case with bottom in convex lense shape, by inserting the plate group so that its stacking side is faced to the outward curved side into the case, and drawing the case so as to change the shape of the convex cross section to a rectangle. CONSTITUTION:A plate group 6 is formed by alternately stacking a positive plate 3 and a negative plate 4 through a separator 5 so that the end of the positive plate is protruded from the upper edge of the plate group and the end of the negative plate from its lower edge. The plate group 6 is put in a metal case 1 from its opening so that the stacking side of the plate group 6 is faced to the outward curved side 2 of the metal case 1. A sealing body in which a metallic cover plate 8 is put in a gasket 7 is put in the opening of the case 1 and placed on the plate group 6. The metal case is pushed up upward through a drawing die D having a guide taper D' to draw inward the outward curved side 2 so as to change the shape of the convex cross section to a rectangle. The opening end of the metal case 1 is bent inward with a crimping die to fix the cover plate 8 through the gasket 7.
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