A disk cartridge which includes a case having an upper wall, a lower wall, and a sidewall, which form an inner receiving space in which a disk is inserted, an opening formed in at least one of the upper wall and lower wall of the case to allow a recording/reproducing unit of a disk drive to access the disk therethrough, and an inlet hole formed at the sidewall of the case to allow the disk to be inserted into and withdrawn from the case therethrough.