A cathode active material includes a lithium composite oxide and a covering material which covers a surface of the lithium composite oxide. The lithium composite oxide is a multi-phase mixture including a first phase having a crystal structure which belongs to a space group C2/m and a second phase having a crystal structure which belongs to a space group R-3m. The lithium composite oxide has an integral intensity ratio I(18°-20°)/I(43°-46°) of not less than 0.05 and not more than 1.15, where the integral intensity ratio I(18°-20°)/I(43°-46°) is a ratio of an integral intensity I(18°-20°) to an integral intensity I(43°-46°). The integral intensity I(α°-β°) is an integral intensity of a first peak which is a maximum peak present within a range of a diffraction angle 2θ of not less than α° and not more than β° in an X-ray diffraction pattern of the lithium composite oxide.