PURPOSE: To form a positive meniscus and enhance the anti-corrosiveness by setting the immersing depth of each electrode plate tab in a preheating vessel, when a bunch of electrode plates is to be welded, so as to be greater than the immersing depth in a molten lead.

CONSTITUTION: When a bunch of electrode plates of a lead-acid battery is to be welded, contaminants on the surfaces of electrode plate tabs 4a, 4b are removed by brushing, followed by removal of surface oxides by washing with a flux, and then the flux is removed and preheating is performed for the tabs. The tabs are immersed in molten lead, followed by solidification. Therein the immersing depth B of each tab in the preheating vessel is made greater than the immersing depth A in the molten lead. This causes the tab to solidify upon through fusion with the lead, to allow formation of positive meniscus in the strap part. Thereby a high reliability strap excellent in the anti-corrosiveness can be fabricated.