A cord angle of reinforcing layers having a bias structure constituting a body portion is set to 25° or more and 45° or less in a neutral state of a body. Reinforcing layers are bonded with a bonding member interposed between the reinforcing layers, the bonding member disposed in a space between the reinforcing layers facing in the cylinder axial direction of the body portion and a hemispherical portion. The layered bonding members have the same bias structure as the reinforcing layers of the body portion. A cord angle of the bonding member is set to ±10° of the cord angle of the reinforcing layers of the body portion. The spaces have a plurality of different sizes. One set of ends of the spaces are set to a plurality of different positions, and the other set of ends are also set to a plurality of different positions.