CATHODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY

To provide a cathode active material capable of reducing cathode resistance of a secondary battery by enhancing electron conductivity thereof without reducing discharge capacity of the secondary battery. Lanthanum compound particles each having a perovskite-type structure are dispersed on surfaces of secondary particles of a lithium transition metal-containing composite oxide and/or in gaps or grain boundaries between primary particles thereof. The lanthanum compound particles have a cross-sectional average particle size of 0.70 μm or less. The number of lanthanum compound particles present per unit area of the cross sections of the secondary particles is 0.03 particles/μmto 0.10 particles/μm, and the number of lanthanum compound particles present per unit area of the surfaces of the secondary particles is 0.01 particles/mμto 0.25 particles/μm. The content of lanthanum with respect to the entire cathode active material is within a range of 0.1% by mass to 5% by mass.