Battery cells are fixed by a cell holder and are housed inside a case in a state where both electrodes are sandwiched by a positive-electrode current collecting plate and a negative-electrode current collecting plate, and springs are arranged above and under the current collecting plates. Claws are provided on side surfaces of the case, which can temporarily fix the springs to the current collecting plates at the time of assembly and prevents the case from being ejected suddenly when a fastener is released at the time of disassembly.