A magneto-optical disk having recording tracks are formed along concentric grooves or a spiral groove. A non-groove region where no grooves are made is provided in a middle part of each recording track. In the non-groove region, there is formed a pit pattern representing information about the recording track. A track-counting U-groove is formed in the non-groove region, for detecting that the light spot of a reading laser beam has moved across the recording track. With the disk thus structured, it is possible to record information at high density and to access a desired recording track at high speed.