A non-aqueous electrolyte secondary battery is provided that has both good safety and durability characteristics while at the same time has high charge/discharge capacity. The cathode active material for a non-aqueous electrolyte secondary battery of the present invention is a lithium nickel composite oxide to which at least two or more kinds of metal elements including aluminum are added, and comprises secondary particles that are composed of fine secondary particles having an average particle size of 2 μm to 4 μm, and rough secondary particles having an average particle size of 6 μm to 15 μm, with an overall average particle size of 5 μm to 15 μm; where the aluminum content of fine secondary particles (metal mole ratio: SA) is greater than the aluminum content of rough secondary particles (metal mole ratio: LA), and preferably the aluminum concentration ratio (SA/LA) is within the range 1.2 to 2.6.