A disk recording/reproducing apparatus includes a chassis rotatably supporting a holder for storing a disk cartridge; an eject lever movably disposed in the chassis in an insertion/removal direction of the disk cartridge and movably in a direction toward or away from the chassis. The eject lever is rotated by being pushed by the disk cartridge 1 inserted into the holder. A cartridge drop preventive mechanism prevents the disk cartridge ejected by the eject lever from dropping from the cartridge holder. The cartridge drop preventive mechanism is formed from a flat spring disposed on one side surface of the holder and makes a sliding contact with one side surface of the disk cartridge during unloading of the cartridge so as to give the disk cartridge a braking force. This arrangement can prevent the disk cartridge from jumping out and dropping off from the cartridge holder during ejection.