An optical disk device including a tray in which recording mediums having differing outer diameters can be selectively mounted. The tray carries the recording media into the main body of the optical disk device wherein it is, chucked by a turntable. Holding members for holding the recording medium at a predetermined position relative to a mounting face of the tray are provided in a front portion and a rear portion respectively relative to the transport direction of the tray. At least one of the holding members is movable between a first holding position for holding a small diameter recording medium, and a second holding position for holding a large diameter recording medium. The holding member is biased toward the first holding position by a biasing member.