According to one embodiment, a magnetic disk device includes a plurality of magnetic disks, a plurality of magnetic heads provided correspondingly to the plurality of magnetic disks and configured to carry out read/write of data from/to the magnetic disks, and a control section configured to control read/write of the magnetic heads. Each of the plurality of magnetic disks includes a first storage section storing therein control information concerning read/write of the magnetic head. The control section switches the first storage section which is a storage destination of first information that is at least a part of the control information from the magnetic disk to another magnetic disk.