Abstract: Elimination of mis-detection of a front erasure section of reference information for controlling the position of a read/write head on the disk storage device is accomplished, by zoning a part of a disk surface for a specific zone RZ separately from a data storage zone DZ, storing a dummy data Dd in a code pattern with a predetermined repetition cycle in an entire area, excluding areas for reference information storage, of the specific zone RZ, and positioning a read/write head in the specific zone RZ to detect a front erasure section ER of the reference information RI by a reference information read out means 30. The read out means 30 reads out of an identification section ID and a servo information section SI of the reference information RI securely without being confused by fake erasure sections.