A magnetic disk apparatus is configured such that a physical track number is converted into an absolute track number by making a track pitch in an absolute track area formed by a given magnetic head wider by a given amount than a track pitch in a corresponding absolute track area formed by a reference magnetic head if the number of absolute tracks is larger in the absolute track area formed by the given magnetic head than in, the absolute track area formed by the reference magnetic head although the number of physical tracks is identical in corresponding physical track areas between different magnetic disks. The given amount is commensurate with an unused area corresponding to a difference in the number of absolute tracks between the absolute track area formed by the given magnetic head and the absolute track area formed by the reference magnetic head.