A secondary battery that can inhibit degradation of an electrode is provided. A flexible secondary battery is provided. A flexible secondary battery includes a positive electrode, a negative electrode, and an exterior body surrounding the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material layer provided over the positive electrode current collector. The negative electrode includes a negative electrode current collector and a negative electrode active material layer provided over the negative electrode current collector. One or both of the positive electrode current collector and the negative electrode current collector have rubber elasticity.