Abstract: A detent structure for a removable disk cartridge comprising a removable cartridge and a receiving seat, the cartridge is fixedly provided in the front thereof with a handle, a press member with a similar shape to that of the handle is provided inside of the handle, the press member is connected with the cartridge by means of a spring and synchronically controls a detent member provided on and protruding out of the cartridge, the detent member also has a spring connecting to the cartridge. The receiving seat has on both sides thereof an engaging hole to allow the cartridge to fit in the receiving seat; the detent member can be firmly engaged therein to prevent the cartridge from drawing out. When the press member is pressed, the detent member is retracted inwardly to relieve engagement of the engaging holes to allow removing of the cartridge. Bearing surfaces are formed inside of the cartridge from rubber sheets connected with the cartridge; therefore, the cartridge has a good vibration-proofing effect.