Disclosed is a thin battery including an electrode assembly in sheet form and a housing for accommodating the electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and an electrolyte layer interposed therebetween. A lubricating material with a lubricating effect is interposed between an inner surface of the housing and the electrode assembly, and is, for example, an inert gas. The inert gas includes, for example, at least one of nitrogen and argon. It is preferable that the lubricating material is present, at least, between end surfaces of the electrode assembly on both sides in the thickness direction thereof and two main flat surfaces of the inner surface of the housing which face the end surfaces, respectively.