A cathode active material capable of increasing a capacity and improving high temperature characteristics or cycle characteristics, a method of manufacturing it, a cathode using the cathode active material, and a battery using the cathode active material are provided. In a cathode active material contained in a cathode, a coating layer is provided on at least part of complex oxide particle containing at least lithium (Li) and cobalt (Co). The coating layer is an oxide which contains lithium (Li) and at least one of nickel (Ni) and manganese (Mn).