Embodiments of the invention compensate for repeatable run-out errors without causing servo system instability. In one embodiment, HDD has a peak filter on a feedback route of a servo system. The peak filter is designed so that a rotating frequency of a magnetic disk, the high-frequency components contained in the rotating frequency and a peak match the rotating frequency and the high-frequency components. Insertion of a required peak filter into the servo system allows compensation for a repeatable run-out (RRO) error due to an event such as a deviation from the roundness of a track. Also, since a Nyquist diagram of the system satisfies required characteristics, a repeatable run-out error may be compensated for without causing instability of the servo system due to use of the peak filter.