A non-aqueous electrolyte secondary battery including a positive electrode core; a positive electrode plate having a positive electrode active material layer formed on the positive electrode core; a negative electrode plate; a flat wound electrode assembly in which the positive electrode plate and the negative electrode plate are wound with a separator therebetween; and a non-aqueous electrolyte, wherein the positive electrode active material is a manganese-containing lithium transition metal composite oxide, the BET specific surface area of the positive electrode active material is 2.0-3.0 m2/g, the total surface area of the positive electrode active material contained in the positive electrode active material layer is 70-90 m2, and the value of A/B is 0.03-0.09 (μmol/m2), where A (μmol) is the total amount of FSO3 contained in the non-aqueous electrolyte, and B (m2) is the total area of the positive electrode active material contained in the positive electrode active material layer.