A disk drive including a lower case, a tray to be attached and detached to and from the lower case while sliding in the lower case and having a turntable on which a disk is seated, and an upper case installed to cover an upper portion of the lower case. The upper case has at least one deviation-prevention element extending toward the lower case to prevent the disk from deviating from the turntable by an external force on the disk drive by reducing a distance between the upper case and the disk seated on the turntable.