<p>A recording medium drive device, comprising a tray inserted into and extracted from the entrance of a casing and on which a cartridge (92) is placed and a retaining member fitted to the casing through a mounting member (40A) and retaining the front end part and the rear end part of the cartridge (92) against the tray. The retaining member further comprises a rotating member (44) fitted to a flat-plate shaped mounting member (40A) rotatably about an axis orthogonal to the inserting and extracting directions of the cartridge (92) and an elastic retaining piece (45) fixed to the rotating member (44) and having the front end part and the rear end part extended from the rotating end part of the rotating member (44). When the cartridge (92) is inserted, the rotating member (44) is operated to separate the front end part of the elastic retaining piece (45) from the cartridge (92), and when the cartridge (92) reaches a specified position, the cartridge (92) is pressed by the both front and rear end parts of the elastic retaining piece (45).</p>
