The compact for a magnetic core is manufactured by filling a soft magnetic powder in the die hole, pressing it to form a compact at a density ratio of the soft magnetic powder being 91% or more, and extruding it from the die hole. Before filling the soft magnetic powder to the die hole, a lubricating coating containing lubricating oil and molybdenum disulfide particles is formed on the inner surface of the die hole. It is more effective when further containing insulating ceramic particles. On the extrusion-sliding surface, the compact has a surface layer of the structure that molybdenum disulfide particles and the insulating ceramic particles are interposed between the soft magnetic powder particles, and insulation of soft magnetic powder particles in the surface layer is not destroyed by extrusion. This provides a powder magnetic core suitable for high frequency application.