PURPOSE: To allow tracking without providing guide grooves by concentrically or spirally executing the crystallization of the crystalline information recording film on a substrate at specified spaced intervals, thereby alternately forming crystalline parts and amorphous parts.

CONSTITUTION: CoFe2O4 is deposited as the recording film 2 by a sputtering method on the quartz glass substrate 1. The crystalline parts and the amorphous parts are alternately formed on the disk when the film is concentrically or spirally crystallized by the laser at the specified intervals. The parts where the information is recorded are, therefore, formed as the crystalline parts and exhibit a magneto-optical effect but the recorded parts remain as the amorphous and since these parts do not exhibit the magneto-optical effect, the parts can play the role of guide. An aluminum film is deposited by evaporation as a reflecting film 3 on the film 2 after the crystallization. The tracking is executed in this way without providing the guide grooves.