In a film-packed battery which stores a battery element (9) with packing films (8a, 8b) and sealed by heat-sealing heat-sealed surfaces of the packing films around the battery element, a heat-sealed portion (6) projecting toward a battery element is provided at part of a heat-sealed portion (5), and a gas releasing portion (7) is formed close to the projecting heat-sealed portion. A pressure safety valve for safely releasing a gas to the outside when the gas is generated in the battery is provided without lowering the reliability of the battery.