In some examples, an electrode plate K is conveyed to a gap 230 of a pair of stacking drums 210 and 220 with a conveying section 100. In synchronization with conveyance of the electrode plate K, the drums 210 and 220 feed a pair of separators S each formed into a predetermined shape with the separators S adhering to corresponding peripheral surfaces of the pair of drums 210 and 220. While feeding the electrode plate K forward in a generally horizontal manner, the separators S are sequentially stacked on both surfaces of the electrode plate K in synchronized with rotations of the drums 210 and 220, and both edge portions of the separators S are welded.