The present invention provides a method of producing a lithium mixed metal oxide, a lithium mixed metal oxide and a nonaqueous electrolyte secondary battery. The method includes a step of calcining a mixture of one or more compounds of M wherein M is one or more elements selected from the group consisting of nickel, cobalt and manganese, and a lithium compound, in the presence of one or more inactive fluxes selected from the group consisting of a fluoride of A, a chloride of A, a carbonate of A, a sulfate of A, a nitrate of A, a phosphate of A, a hydroxide of A, a molybdate of A and a tungstate of A, wherein A is one or more elements selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr and Ba. The lithium mixed metal oxide contains nickel, cobalt and manganese, has a BET specific surface area of from 3 m2/g to 15 m2/g, and has an average particle diameter within a range of 0.1 μm or more to less than 1 μm, the diameter determined by a laser diffraction scattering method.