PURPOSE: To improve an output by adhering a butt faces of both center cores except a part with a prescribed depth of a gap by means of an inorganic adhesives, filling in glass to the part of the prescribed depth of the gap and making the shape of the center cores thick.

CONSTITUTION: A recording/reproducing code 10 and the center cores 11, 18 and an erasure core 17 and the center cores 11, 18 are adhered respectively and the butt faces of both the center cores 11, 18 are adhered by a nonmagnetic adhesives to form a composite magnetic. The butt faces of both the center cores 11, 18 are adhered except a part of a prescribed depth of the gap side by an inorganic adhesives 21, the glass 22 is filled in the part of the prescribed depth of the gap side and the shape of the center cores 11, 18 is formed thick.