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 (D50) 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: Li1+xMn2-x-yYyO4 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%.