With the inventive method, after a servo pattern data including index pattern is written onto the servo disk in a magnetic disk unit, a variety of software processes is effected thereafter, and the servo pattern data having been written is read and the index pattern is detected, a varify data is outputted, the comparison between the read index pattern data and the verify data is started, thereby verifying the validity of the writte servo pattern data. More particularly, immediately after completion of said variety of software processes and without waiting for the revolution of the servo disk, the verify data is compared with the read servo pattern data, whereby the write of servo pattern data onto the magnetic disk and the read verify process can be effected speedily.