When spinel-type lithiated cobalt oxide is employed for a cathode active material for a lithium ion battery, a sufficient discharge capacity is not always obtained. Thus, spinel-type lithiated cobalt oxide is doped with at least chromium, and specifically, a cathode active material for a lithium ion battery includes a spinel-type crystal phase including lithium, cobalt, chromium and oxygen, and the cathode active material has a composition represented by LiCoxCryMzO2±δ where M is at least one selected from Al and Mn, and 0.85≤x