PURPOSE: To perform stable tracking, by forming a tracking guide and a pit for signal information which are equal in the difference in level from a flat surface and different in width from each other.

CONSTITUTION: The tracking guide 2 is provided on a recording layer 1 and the pit for signal information 3 is formed on this tracking guide 2; the both are equal in the difference in level (depth) from the flat surface. Further, the width of the tracking guide 2 is less than such a value that the level of reflected light from the tracking guide 2 approximates the level of reflected light from the flat surface, e.g. 0.6W0.8μm regarded conventionally as optimum, so the total intensity of light reflectilon from a spot of read laser light is increased to approximate the level of light reflection from the flat part, and the difference from the level of light reflection from the pit 3 for signal information increases to improve the S/N ratio of signa reading.