According to an embodiment, a magnetic disk device includes a magnetic disk, a magnetic head, and a control circuit. The magnetic disk has a plurality of first storage regions disposed in the radial direction. The recording method is changeable for each of the plurality of first storage regions. The control circuit operates such that, when having received a first command instructing to change the recording method of one first storage region out of a plurality of first storage regions, the control circuit changes the recording method of the one first storage region in accordance with the first command, and moves a magnetic head onto the second storage region before receiving a second command.