wherein the data tracks are formed as data track groups by said multi-channel type head unit in regions sectioned with the servo tracks in the width direction of the magnetic tape, and each data track group formed respectively with one of said plurality of servo tracks, and

wherein each data track group comprises more than three data track sub-groups comprising a plurality of data tracks having the same track width, respectively, and aligned in the width direction of the magnetic tape, with data tracks of a first data track sub-group located closest to a respective one of said plurality of said servo tracks having the smallest width size, while data tracks of a second data track sub-group located most distant from the respective one of said plurality of said servo tracks having a largest width size, and data tracks of more than one data track sub-group located between the first and second two data track sub-groups having a width of intermediate value between said largest and smallest widths.