A disk drive includes a main frame; a cartridge slidably installed in the main frame; a plurality of trays stacked in the cartridge and slidably installed therein; an elevation unit for controlling a height of a turn table; a tray selecting unit for locking each tray to a state that each tray can be loaded or unlocking a specific tray among a plurality of locked trays to draw it out of the main frame; a loading unit for loading the specific tray, among the plurality of trays locked by the tray selecting unit to reproduce/record a disk by means of an optical pick-up unit, onto the turn table; and a driving unit for driving the cartridge, the elevation unit, the tray selecting unit and the loading unit.