Abstract: An object of the invention is to provide an inexpensive non-aqueous electrolyte secondary battery that allows reversible charge and discharge to be carried out and can be used for a long period because of a stable non-aqueous electrolyte used therein. The invention provides a non-aqueous electrolyte secondary battery including a positive electrode including a positive electrode active material and capable of storing and releasing sodium, a negative electrode capable of storing and releasing sodium, and a non-aqueous electrolyte, and the positive electrode active material includes sodium, nickel, manganese, and a transition metal that can exist in a hexavalent state. An example of the transition metal that can exist in a hexavalent state may include tungsten (W). An example of the negative electrode may include a sodium metal capable of storing and releasing sodium ions.