The present invention provides a battery capable of suppressing or avoiding degradation of a positive electrode due to heat applied in thermal welding of separators, and of preventing short circuit through the welded portions. A battery (10) of the present invention includes a packaged positive electrode (40) made by placing a positive electrode (50) in a package formed by joining at least part of end portions of a separator (60) together by thermal welding; and a negative electrode (30) being larger than the positive electrode (50) and stacked on the packaged positive electrode (40). Welded portions of the separator (60) formed by the thermal welding are provided outside an outer periphery of the negative electrode (30), when seen in a stacking direction.