PURPOSE: To greatly improve a fine particle magnet in coercive force, energy product and the like, by a method wherein when Mo-Sb-Bi alloy fine particles are molded, they are subjected to a predetermined heat treatment either before, during or after the molding.

CONSTITUTION: When a molded article is obtained by casting a slurry obtained by adding an organic solvent or the like to Mn-Sb-Bi alloy fine particles having a composition consisting of 29W52% Sb, not larger than 15% Bi and the balance substantially Mn by atomic ratio, or pressing or injecting such fine particles, the slurry or the fine particles are heat-treated for about 0.5W20hr at 300W800°C, more preferably 400W750°C either before, during or after the molding. As the atmosphere for the heat treatment, an inert gas atmosphere or a vacuum is desirable. Simultaneously with or after the heat treatment, sintering is effected for about 0.5W10hr in an atmosphere of an inert gas or the like or in a vacuum at 200W800°C.