The present invention provides a highly reliable energy storage device. An energy storage device (10) includes an electrode assembly (160) in which a positive electrode plate (163) and a negative electrode plate (164) are stacked, and a positive electrode current collector (140) connected to a positive-electrode-side end portion (161) of the electrode assembly (160), wherein the positive-electrode-side end portion (161) of the electrode assembly (160) includes: (a) an electrode plate welded portion (161a) at which the stacked positive electrode plate (163) are welded in a stacking direction and not joined to the positive electrode current collector (140); and (b) a current collector joined portion (161b) which is joined to the positive electrode current collector (140) and is arranged adjacently to the electrode plate welded portion (161a) in a direction that intersects with the stacking direction.