Abstract: A battery sealing structure is provided, which can provide an excellent seal for a battery. The sealing structure has an explosion-proof function and contributes to improved battery assembling operation efficiency. A three-part stack, including a cap member (3), a PTC element (4) and a safety valve (5), is inserted in a gasket (8). The safety valve has the same outer diameter as the cap member (3) and has a breakable portions capable of being broken in the event of an increase of pressure in the battery. The gasket (8), made of a soft synthetic resin, is inserted in a battery housing (2). The stack is set on an upper surface of a stepped portion (8a) of the gasket such that its outer edge is in close contact with the inner periphery of the gasket.