PURPOSE: To increase recording density and to reduce cross talk between tracks by recording information in a first track and a second track with different modulation systems respectively.

CONSTITUTION: For example, a PE(Phase-Encoding) modulation being one of digital modulation systems is applied as a first modulation system, a RLL(Run- Length-Limited) modulation being one of digital modulation systems is applied as a second modulation system. Thereby, ID1, ID2 of sectors 13, 17 are arranged in the direction of a radius, though cross talk of -15 dB approximately is generated in an ID section, since demodulation systems of the ID1 and ID2 signal reproducing circuits are different, the circuit is not affected by cross talk, respective ID signals can be normally reproduced.