PURPOSE: To manufacture magnetic super fine particles having small variance of particle diameters by executing plasma treatment to the mixed powder containing iron and silicon.

CONSTITUTION: To the mixed powder containing iron and silicon or alloy powder containing iron and silicon, the plasma treatment is executed. Then, in the case of using FexSi1-x for the raw material powder composed of the iron and silicon, (x) is set to about 0.200-0.999, according to the use and if necessary, Co, Mn, etc., may be contained. Further, by suitably controlling the plasma treatment, the particle diameter can be controlled to over the wide range of about 50-5000. By this method, the magnetic super fine particles, which is suitable to thermoelement, magnetic body, etc., is manufactured at the narrow particle diameter variance and good controllability.