Abstract: A disk cartridge loading and ejecting mechanism for a recording/reproducing apparatus has: a cartridge holder for receiving a disk cartridge which is movable between a cartridge loading position and a cartridge ejecting position; a loading lever for moving the cartridge holder to the cartridge loading position; a protrusion provided at a side portion of the loading lever and moved integrally with the loading lever; a lock lever having an engagement portion with which the loading lever engages and an abutting portion on which a forward end of the disk cartridge is able to abut and for locking the loading lever in the ejecting position and the loading position; a sliding plate having a first and a second slanting cam portion with which the protrusion is engageable and being movable in the direction along which the disk cartridge is inserted and discharged; an ejection operation section connected to the sliding plate for moving the sliding plate in the disk cartridge insertion direction; and an elastic member fo