Abstract: A positive electrode active material for high voltage lithium battery which is represented by general formula LixMn2−yMyO4 LixMn2−yMyO4 (M: a 2-valency metal (Ni, Co, Fe, Mg, Zn), with 0.45≦y≦0.60, 0≦x≦1) having cubic spinel structure of lattice constant within 8.190 angstrom. Such an active material is manufactured by employing sol-gel process wherein one of inorganic salt, hydroxide and organic acid salt of lithium or a mixture of these for Li, one of inorganic salt and organic acid salt of manganese or a mixture of these for Mn, and one of inorganic salt and organic acid salt of the selected metal or a mixture of these for M are used as the starting materials for synthesis, ammonia water is added to the solutions of these starting materials in alcohol or water to obtain gelatinous material and the gelatinous material thus obtained is fired.