According to one embodiment, a magnetic disk device includes a disk having a first region to which data is written by normal recording and a second region to which data is written by shingled recording, a head configured to write the data to the disk and read the data from the disk, and a controller configured to, when first data and second data is to be sequentially written to a third region of the second region, reserve a fourth region corresponding to the first data and the second data in the first region, write the first data to the fourth region, write the second data after the first data in the fourth region, and sequentially write the first data and the second data read from the fourth region to the third region.