Information is optically recorded to a recordable optical disk by a light beam, and a return light is received from the recordable optical disk to produce a tracking error signal. The recordable optical disk includes: a substrate having a disk shape; a groove formed on a surface of the substrate along a predetermined track which the light beam is made to follow; and a recording layer formed on the surface of the substrate, to which the information is recorded by the light beam. A depth of the groove is prescribed such that an amount of the return light from the groove becomes smaller than an amount of the return light from the portion of the recording layer other than the groove in a condition after recording.