A positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention includes composite oxide particles including lithium, nickel, and an element M, the element M being at least one of aluminum and cobalt. The composite oxide particles include primary particles and each particle of the primary particles includes a surface portion and an inner portion. A content of the element M in the surface portion is higher than a content of the element M in the inner portion, and a proportion of the primary particles relative to all of the composite oxide particles is 80 to 100 wt %. According to the invention, a positive electrode active material for a non-aqueous electrolyte secondary battery that has excellent cycle characteristics and storage characteristics and is suitable for use in a wide range of the state of charge and in a high-temperature environment and a non-aqueous electrolyte secondary battery using the same can be obtained.