In a non-aqueous electrolyte secondary battery comprising: a negative electrode containing, as a negative electrode active material, at least a material capable of absorbing and desorbing lithium ions or metal lithium; a positive electrode; and an electrolyte, an oxide containing nickel and manganese elements, the material comprising primary particles of the oxide having a twining portion and a superlattice arrangement of a [√{square root over (3)}×√{square root over (3)}] R30° when assigned as R3-m is used as a positive electrode active material.