PURPOSE: To introduce nitrogen into crystal structure without decomposition, by preparing alloy so as to have an average grain diameter and average crystal grain diameter containing one kind of rare earth element containing Y and one kind of transition metal element, with ThMn12 type crystal structure, and performing nitriding reaction by heating the alloy in nitrogen gas.

CONSTITUTION: RFe11M alloy [R (rare earth) = Sm, Nd, Pr, M=Ti, Mo, V] having ThMn12 type structure is prepared by a high frequency melting method, and annealed at a temperature 1373K or lower for 10-300 hours to make alloy composition uniform. Thereby crystal grain diameter is prepared. After the crystal is ground into particles whose diameter is 10μm or smaller, particles whose diameters are 2-3μm or smaller are eliminated by using an air flow winnowing apparatus or the like. Thereby powder whose diameters are in the range of 2-10μm is prepared. After the powder is heated up to 300°C in hydrogen gas, cooling down to a room temperature is sufficient. As to nitriding after that, a necessary nitrogen amount can be obtained by treatment in nitrogen gas at 300-350°C for 1-10 hours, and stable uniform magnetic material can be manufactured.