PURPOSE: To prevent the generation of short circuit and mixing of positive and negative active materials and to enhance productivity by enveloping at least a positive plate and a negative plate with a tape-like separator, and by folding up in the separator bonded part between both plates.

CONSTITUTION: A square type battery is fabricated by inserting an electrode group obtained by alternately stacking positive plates and negative plates into a battery case, then by filling an electrolyte. The electrode group is assembled in such a way that plural positive plates 3 are put in bags formed by ultrasonic welding a long sheet separator 4 and folded up in bellows and each negative plate 5 is inserted into the folding up part, then electrode plates are alternately faced and stacked. Leads 8, 16 from each plate are stacked and connected. Performance drop caused by mixing of active material powder from the plate 3 and the plate 5 is prevented and the capacity of the battery is increased by narrowing the connecting width.