PURPOSE:To increase the accuracy of size and the mechanical strength, and to increase the sensitivity in reproduction, by providing a plurality of skew grooves through cutting off of one ridge of a magnetic gap constituting surface with a slope and a suitable width at a prescribed interval in parallel. CONSTITUTION:A magnetic head core is made of a manganese-zinc ferrite having 103X10<-7>/ deg.C of thermal expansion coefficient, and a groove is given to one surface of the core with a slope, and a paste mixing 50% of glass powder, 600 deg.C of softening temperature and 108X10<-7>/ deg.C of thermal expansion coefficient, 3% of polyvinyl alcohol, and 47% of water is coated on the groove. The groove is heated at 830 deg.C under nitrogen atmosphere including 0.01% of oxygen, the glass powder is molten and filled in the groove. Next, excessive glass is shaped off on the magnetic gap constituting surface of the magnetic head core and the surface is finished to a mirror surface. Further, mirror polish is made for another ferrite core, silicon oxide is sputtered on the entire surface of the magnetic gap groove A surface, 0.8mum thick to form a non-magnetic substance layer. A pair of ferrite cores are laminated, and heated at 750 deg.C under nitrogen atmosphere, both the ferrite cores are bonded incorporatedly and they are cut and polished to one track thickness.