An information recording medium for reproducing information by irradiation with
a laser beam condensed by an objective lens with a numerical aperture NA includes
a disk-shaped substrate and a recording layer disposed on the substrate. On the
surface of the substrate, a plurality of prepit regions and a plurality of data
regions are disposed alternately along spiral or concentric virtual track centers.
Each prepit region includes a pair of wobble pits for tracking servo, and a length
L (m) of the wobble pit along the virtual track center, a wavelength
(m) of the laser beam, and a numerical aperture NA satisfy a relationship:
0.3L. NA/0.65.