PURPOSE: To obtain a magnetic core for high frequencies able to prevent short- circuit between layers during the cutting operation and to reduce the external stress during the fixing operation, by winding an amorphous magnetic thin strip such that an adhesive agent is impregnated only between the layers to leave both the inner and outer surfaces of the thin strip uncovered.

CONSTITUTION: An amorphous magnetic thin body 1 is wound to shape a torus and subject to heat treatment at as high temperature as possible but lower than the crystallization temperature of amorphous substances in order to separate the fine crystalline phase. Subsequently, an epoxy resin 2 as an adhesive agent is impregnated into the core, while the inner and outer sides of the core are covered with clay so that no resin is laid thereon. After the resin cures, the core is cut off diametrically with a magnet blade. Thereby, the short-circuit between the layers during the cutting operation can be prevented, and the external stress can be reduced by inhibiting the magnetic walls from permanent fixation during the fixing operation. Thus, the core loss at higher frequencies can be reduced effectively.