A secondary battery with improved flexibility. The secondary battery includes: a substrate; a first electrode collector integrally formed with the substrate as one body; a first electrode material mixture layer; an electrolyte layer; a second electrode material mixture layer; and a second electrode collector having a metallic mesh structure integrally formed with the second electrode material mixture layer as one body, wherein the first electrode material mixture layer, the electrolyte layer, and the second electrode material mixture layer are sequentially formed on the first electrode collector in this order.