<p>The main purpose of the present invention is to provide a thin secondary battery which is capable of efficiently dissipating the heat generated within the battery to the outside, while having improved energy density. A thin secondary battery of the present invention is provided with an electric power generating element (10) in which positive electrode plates (12) and negative electrode plates (14) are laminated with separators (5) being interposed therebetween. In the electric power generating element (10), the outermost positive electrode plate (12) is configured such that the outside surface of a positive electrode collector (2) is provided with a first resin layer (6a) instead of a positive electrode active material layer (1) and the outermost negative electrode plate (14) is configured such that the outside surface of a negative electrode collector (4) is provided with a second resin layer (6b) instead of a negative electrode active material layer (3). The first resin layer (6a) and the second resin layer (6b) cover the electric power generating element (10), and the first resin layer (6a) and the second resin layer (6b) are joined with each other at a peripheral portion (9) of the electric power generating element (10), thereby hermetically sealing the electric power generating element (10).</p>
