A film-packed battery includes a battery element and a packing film which houses the battery element and includes a main heat-sealed portion which is formed around the battery element, and a projecting heat-sealed portion which projects from the main heat-sealed portion toward the battery element, and a gas releasing portion formed in the projecting heat-sealed portion and the main heat-sealed portion adjacent to the projecting heat-sealed portion, wherein a distal end of the gas releasing portion reaches the projecting heat-sealed portion and the gas releasing portion connects external air with a heat-sealed interface of the packing film.