To provide a method of demagnetizing a magnetic tape that can completely remove the remanent magnetization even when the magnetic tape has a large coercive force.

The method of demagnetizing the magnetic tape has a first demagnetizing step to place the pancake 10 in the attenuating ac magnetic field generated inside an air core coil connected in series to a dc power supply using a capacitor making the winding axis Ax substantially perpendicular to the direction of the magnetic flux MF1 of the attenuating ac magnetic field, and a second demagnetizing step to move the pancake 10 processed in the first demagnetizing step away from the ac magnetic field after exposing it to the ac magnetic field making the winding axis Ax direction substantially the same as the direction of the magnetic flux MF2 of the ac magnetic field.

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