Embodiments of the invention provide a magnetic disk drive that exhibits excellent overall stability of a feedback control system even when the preset frequency for a peak filter significantly changes. In one embodiment, the symbol P denotes a VCM model, which outputs a head current position signal. The symbol C denotes a controller. The controller inputs a position error signal PES that is derived from a head current position signal output from the P, and outputs to addition point a control signal of a drive device for moving a magnetic head. Signal x to which disturbance noise is added enters a peak filter. The output y from the peak filter is output to addition point via a phase determination filter and added to a control signal output from the controller. A phase comparison frequency updater compares the phase of the position error signal against the output signal phase of the peak filter, changes the preset frequency for the peak filter in accordance with the result of comparison, and changes a transfer function for peak filter phase determination in accordance with a change in the preset frequency.