An optical disk including a disk substrate having guide grooves in one of a spiral shape and a concentric shape, and pits formed between adjacent guide grooves according to predetermined information signals such as address information signals, etc. An optical recording layer is formed in the shape of a thin film on the disk substrate. The guide grooves have a depth ranging from about .lambda./8 to about .lambda./4 and the pits have a depth ranging from about .lambda./4 to about .lambda./2, where .lambda. is a wavelength of a reproducing light beam.