To simplify a welding process of a lead battery and improve productivity.

After inserting bottom part alone of a laminated body for three cells in a partition of a battery case 4 of adjoining group, a welding electrode pillar 5, a cast-on welding part 8 and an electrode pillar 2 are formed on an ear part of the laminated body 6. After the welding by the cast-on method, the laminated body 6 is inserted to the dead end of the partition. By repeating the process with other cells of partitions of other groups, six cells are connected in series by resistance welding the electrode pole pillar parts 5 for welding.