The present invention provides a magnetic core whose outer surface has been coated without handling brittle ribbon to thereby impart insulating properties and shape retention properties to the magnetic core after annealing heat treatment, and further provides an adhesive resin composition for a magnetic core, which is useful for efficiently producing the above-mentioned magnetic core without using any organic solvent and which per se is stable to heat and elapse of time. By forming a coating film having a certain thickness or more on an outer surface using a composition containing a resin of specific properties, there can be obtained a magnetic core whose outer surface has been coated without handling brittle ribbon to thereby impart insulating properties and shape retention properties to the magnetic core after annealing heat treatment. The adhesive resin composition containing particles of a resin having specific properties is useful for efficiently producing the above-mentioned excellent magnetic core without using any organic solvent, and this composition is stable to heat and elapse of time.