Abstract: A thin secondary battery with a power-generating element 10 including positive electrode sheets 12 and negative electrode sheets 14 stacked with separators 5 interposed therebetween, wherein the outermost positive electrode sheet 12 of the power-generating element 10 includes a first resin layer 6a, instead of a positive electrode active material layer 1, on an outer surface of a positive electrode current collector 2, the outermost negative electrode sheet 14 of the power-generating element 10 includes a second resin layer 6b, instead of a negative electrode active material layer 3, on an outer surface of a negative electrode current collector 3, and the first and second resin layers 6a and 6b cover the power-generating element 10, and are bonded to each other at peripheral portions 9 surrounding the power-generating element 10, thereby hermetically sealing the power-generating element 10.