Zn layer 21 or Zn alloy layer, Ni layer 22, and Sn layer 23 or Sn alloy layer are formed on a connecting terminal part 10a of a positive electrode composed of Al by plating. Accordingly, this can solder Cu negative electrode, which is composed of metal that is different species from Al, through Sn layer 23 or Sn alloy layer so that jointing strength of the Al positive electrode and the Cu negative electrode can be enhanced. Further, since the contacting area is increased in comparison with the conventional jointing by the spot-welding or the conventional fastening by a bolt so that the resistance value at the contacting point is reduced, the voltage drop of the energy storage device by contact resistance can be reduced.