To enhance reliability of connection between an electrode of each unit cell and a lead-out lead wire for voltage detection for example, save cost in wiring work, and enhance safety.

This device 1 has an intercell bus bar 9 for connecting in series a plurality of unit cells 2 to which a positive electrode cover and a negative electrode cap are fixed, and a terminating bus bar 11 for connecting a terminating unit cell 2 and a cable 12 connected to an outside output terminal, and a corrugated part formed by folding up a plane-shaped part and a connecting part formed by closely tightening the end are formed in the terminating bus bar 11. In the device 1, a voltage detecting wire 14 is welded directly or through a rod-like crimp-style terminal to the positive electrode cover or the negative electrode cap of the unit cells 2 by applying pressure with a welding electrode.