Disk device having conventional magnetic recording region and shingled magnetic recording region of different linear density

A magnetic disk device comprising:

• a disk having, in a first region segmented in a radial direction, a plurality of first tracks which are written with a space in between in the radial direction at a first linear recording density and a plurality of second tracks which are written on top of one another in the radial direction at a second linear recording density less than the first linear recording density;
• a head which writes data to the disk and reads data from the disk;
• and
• a controller which executes at least one of conventional recording processing which writes a plurality of tracks with a space in between in the radial direction and shingled recording processing which writes a plurality of tracks on top of one another in the radial direction, wherein
• the controller executes the shingled recording processing at the second linear recording density and at a track density at which a product of the second linear recording density and the track density becomes maximized in the first region.