Abstract: A magnetic disc apparatus employing a constant-density recording type and a magnetic disc driver for accessing data thereon. The magnetic disc apparatus comprises a plurality of tracks extended in a circumferential direction on the magnetic disc apparatus surface; a plurality of servo and data information areas which are provided in the circumferential direction of each track; a WID (wedge identification) field for recording the ID for data sectors positioned in one data information area, the ID being recorded in only one interval for each data information area; and a PID (pseudo identification) field positioned in front of each data sector and having an interval corresponding to transfer time of the PID (i.e. the ID of a corresponding data sector) generated from a WID field during access of the magnetic disc apparatus.