A magnetic core for a flying-type composite magnetic head, including a pair of core pieces, a glass portion for bonding the core pieces, and a thin magnetic metal layer of Fe-Al-Si alloys formed on at least one of opposing surfaces of the core pieces. The thin magnetic metal layer extends by 10 .mu.m or more from an apex of a magnetic gap defined by the core pieces and has an inner end existing by 15 .mu.m or more inside an inner end of the bonding glass portion.