In some examples, an electrode plate (K) is conveyed to a gap (230) of a pair of stacking drums (210, 220) with a conveying section (100). In synchronization with conveyance of the electrode plate (K), the drums (210, 220) feed a pair of separators (S, S) each formed into a predetermined shape with the separators (S, S) adhering to corresponding peripheral surfaces of the pair of drums (210, 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, 220), and both edge portions of the separators (S) are welded.