PURPOSE: To obtain a magnetic head which can be easily produced with high accuracy secured for measurement of depth of a magnetic gap, by burying a detector into the nonmagnetic part of a magnetic head to detect the depth of the magnetic gap.

CONSTITUTION: A track width prescribing groove 2 is formed with a prescribed space to a single polished side 1a (1b) of a ferrite block 1A (1B), and the glass 3 of a high melting point is filled into the groove 3. Then the surface 1a (1b) is polished (process III). A marker 5 is formed on the glass 3 of the block 1A in the form of an isosceles triangle having 40μm height and bottom side by a photoresist process. A nonmagnetic film is formed on the surface 1a and polished so that the recess part 8 of the marker remains. Thus a detector 10 is obtained. Then a winding groove 10 coincident with the apex of the detector 10 is formed together with a groove 13 containing a glass rod having a low melting point and a spacer film 14. The block 1B of the process III is joined to the groove 13 via said glass rod. Then the block 1B is cut with width L to obtain a magnetic head A. The depth D of a magnetic gap can be measured with high accuracy by the detector 10.