PURPOSE: To enhance the adhesion between a lug and a foot lead to prevent the corrosion of a negative electrode plate lug and a strap part and improve productivity by roughening an engraved part surface.

CONSTITUTION: An engraved part surface 2 of a cast-on-strap mold 1 is subjected to roughening. By roughening the surface 2, an air layer, though being a little, is provided between a molten lead alloy poured into the mold 1 and the mold surface 2. Accordingly, abrupt lowering of temperature of the poured molten lead alloy is prevented and appropriate melting of a lug 3 is expedited so as to enhance adhesion between the lug 3 and a foot lead 4 and prevent the generation of a gap between the lug 3 and the foot lead 4. Consequently, a negative electrode plate and a strap part 5 are hardly corroded and a highly reliable casting mold can be provided.