To prevent lowering of coercive force in heating by coating the surface of R-T-M-N compound fine-pulverized powder having dine-pulverized ThMn12 stricture having a specific average particle diameter, with a specific amount of Zn, and heat-treating the powder.

Coarse-pulverized powder has at least 90vol% of ThMn12 structure with particle diameters of 150μm or less and has a composition including 7.0-9.0at% of R (R: one or more of rare earth elements including Y and including 50% or greater of one or two of Or and Nd), 74.0-89.5at% of T (T: Fe or a part of Fe replaced with 30% or less of Co), and 3.5-16.0at.% of M (M: at least one of Ti, V and Mo). The coarse-pulverized powder is heated at 350-550°C for 5-50 hours in a gaseous mixture including 1-95% partial molar quantity of H2 and the residue N2, under the pressure of 0.2-10atm, and the powder is cooled. Then, the power is fine-pulverized in an inert gas such that the powder includes 80wt.% or greater of particles having diameters of 1-5μm. Then the powder is coated with 1-500mg/m2 of Zn, and the coated powder is heat-treat at 300-450°C in the inert gas atmosphere.