PURPOSE: To eliminate almost areas where data is left unerased or is overerased, by arranging a tunnel erase magnetic head so that an R/W gap and an erase gap are always placed on both sides of the line passing the rotation center of a disc and their positions are equally distant from this line.

CONSTITUTION: The tunnel erase magnetic head is so arranged that an R/W gap 1 and an erase gap 2 are always kept equally distant from a line 5 passing the rotation center of the disc. Then, auxiliary lines 6 connecting both ends of the gap 1 and both inside ends of the gap 2 are superposed on a track 7 in positions where gaps 1 and 2 are placed, and the part, where data is left unerased or is overerased, of the track 7 due to the gap 2 is eliminated approximately completely. Further, even if the magnetic head is moved along the line 5, the part where data is left unerased or is overerased is not generated in all tracks.