A cathode active material capable of further improving chemical stability, a method of manufacturing the cathode active material, and a battery using the cathode active material are provided. The cathode includes a cathode active material in which a coating layer made of a compound including Li, at least one selected from Ni and Mg, and O is arranged on complex oxide particles represented by Li1+xCo1−yMyO2−z, where M is at least one kind selected from the group consisting of Mg, Al, B, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Mo, Sn, W, Zr, Y, Nb, Ca and Sr, and the values of x, y and z are within a range of −0.10≦x≦0.10, 0≦y