When positioning information is previously written in a disk-shaped recording medium, used for positioning a head provided for writing information to the disk-shaped recording medium or reading information written in the disk-shaped recording medium, the positioning information for one track of the disk-shaped recording medium includes, along a path of the one rotation, an overlapping part by which the head can be re-directed to the non-overlapping part if the head is offset from its starting point when it reaches the end of the rotation.