This invention provides lithium manganate which has a high output and is excellent in high-temperature stability. This invention relates to lithium manganate particles which are produced by mixing a lithium compound, a manganese compound, a Y compound and an A compound and then calcining the resulting mixture, and have a composition represented by the following chemical formula 1 and an average secondary particle diameter (D50) of 1 to 15 μm, in which Y is at least one element selected from the group consisting of Al and Mg; A is a sintering aid element having a melting point of not higher than 850° C.; x and y satisfy 0.03≤x≤0.15 and 0≤y≤0.20, respectively; z is in the range of 0 to 2.5 mol % based on Mn, wherein the lithium manganate particles have a sulfur content of not more than 100 ppm. Li1+xMn2-x-yYyO4zA  (Chemical Formula 1)