A storage device includes a predetermined number of disks on which servo information is recorded, and a predetermined number of heads. The heads are positioned on target cylinders on the basis of the servo information read from the disks through the heads, so that information recording/reproducing can be performed. The disks include outer guard band areas located further out than data areas and inner guard band areas located further in than the data area. Analysis information concerning disk surfaces are recorded on the outer guard band areas. Each of the outer guard band areas is segmented into first and second outer guard band areas in a radial direction. The analysis information is recorded on the first outer guard band area. The servo information for an off-track correction is recorded on the second outer guard band area.