To provide a method with which the inner peripheral end face of a circular hole is easily and satisfactorily polished, even when the diameter of the circular hole in the center part of a disk substrate is reduced, and with which a large quantity of disk substrates with stable quality is supplied at a low cost, occurrence of thermal asperity difficulty and head crash in a magnetic disk are prevented, and the density of the information recording surface of the magnetic disk is increased.

In the process for polishing the inner peripheral end faces of circular hole 1 at the center part of disk substrate 2, a magnetic field is formed on the inner peripheral sides of the circular holes 1, abrasive materials 4 including magnetic particles and abrasive grains are held by the magnetic field in the circular hole, and the magnetic field is moved to the inner peripheral end face of the circular holes 1 to move the abrasive materials 4 to the inner peripheral end face of the circular hole 1 for polishing the inner peripheral end face of the circular hole by a magnetic polishing method.