<p>An optical disk cartridge capable of receiving an optical disk having a substrate and a light transmitting layer thinner than the substrate and of controlling its warping to within predetermined limits. An optical disk cartridge (32) has an opening (20) on one thickness-wise side and an opening (34) on the other side, the area of each of these openings being not less than 1/4 of the area of an optical disk (16). Further, the ratio of the area of the opening (20) to the area of the opening (34) is from 1/4 to 4.</p>
