The present invention aims at providing lithium manganate having a high output and an excellent high-temperature stability. The above aim can be achieved by lithium manganate particles having a primary particle diameter of not less than 1 µm and an average particle diameter (D 50 ) of kinetic particles of not less than 1 µm and not more than 10 µm, which are substantially in the form of single crystal particles and have a composition represented by the following chemical formula: Li 1+x Mn 2-x-y Y y O 4 in which Y is at least one element selected from the group consisting of Al, Mg and Co; x and y satisfy 0.03 ≤ x ≤ 0.15 and 0.05 ≤ y ≤ 0.20, respectively, wherein the Y element is uniformly dispersed within the respective particles, and an intensity ratio of I(400)/I(111) thereof is not less than 33% and an intensity ratio of I(440)/I(111) thereof is not less than 16%.