In the present invention, the electrode assembly is first formed, and then a tab portion is formed by compressing an active material unfilled portion in an electrode having a foamed-metal electrode substrate (Tab Portion Formation Step). Accordingly, in the manufacturing method of the present invention, even if winding misalignment is created in which the edge of the separator is located adjacent to one edge of the active material unfilled portion during the formation of the electrode assembly, the misaligned portion of the separator is pushed in the width direction of the electrode together with the active material unfilled portion when the compression is applied in the Tab Portion Formation Step. Herewith, it is less likely to tuck a part of the separator between the tab portion and the current collector when the current collector is joined in the Current Collector Joining Step.