A battery includes a plurality of flat type batteries and a connector member that electrically connect the plurality of flat type batteries to one another. Each of the plurality of flat type batteries is provided with an outer sheath having a composite laminate film, an electric power generating component, which includes a positive electrode plate, a separator and a negative electrode plate and is accommodated in the outer sheath by compelling at least a part of a circumference of the outer sheath to be joined by thermally welded portions, a positive-electrode terminal lead conductive with the positive electrode plate and held between the thermally welded portions, and a negative-electrode terminal lead conductive with the negative electrode plate and held between the thermally welded portions. At least one of the positive-electrode terminal lead and the negative-electrode terminal lead has a surface covering layer made of a metal different from that of its terminal mother material.