Magnetic disk device and write method

According to one embodiment, a magnetic disk device includes a memory, a disk including track groups each including overlapping tracks, a head including a write head, and a read head, and a controller configured to write first position data, including a first position error of the write head with respect to a first target track, to the memory and a second recording area subsequent to a first recording area to which first data is written, when writing the first data to the track groups, to read the first position data from the memory or the second recording area when adding data after writing the first data, and to control a position of the write head based on the first position data.