A disk drive includes: a pair of guide walls, which is arranged in the vicinity of the holder opening of a cartridge holder to define a direction in which a disk cartridge is supposed to be inserted; a first opening/closing lever, which has a first engaging portion that engages with a portion of the disk cartridge and which rotates while the disk cartridge is being inserted or ejected; and a second opening/closing lever, which has a second engaging portion that engages with another portion of the disk cartridge and which rotates while the disk cartridge is being inserted or ejected. The first and second opening/closing levers rotate so as to leave a broader gap between the first and second engaging portions than between the guide walls when the drive gets loaded with the disk cartridge, thereby opening a window in the disk cartridge.