A disk apparatus includes a tray that moves with respect to a chassis fixed to an apparatus body to carry a disk, a drive unit that moves in a direction substantially orthogonal to the carrying direction of the tray with respect to the chassis to mount or dismount the disk placed on the tray, a pickup unit provided on the drive unit and having an optical pickup for recording or reproducing the disk, the pickup unit being movable in a radial direction of the disk, and a motor which is arranged on the drive unit and drives the drive unit, pickup unit and tray through a plurality of gears. A worm gear is attached to a motor shaft of the motor. Lead angle of the worm gear is set at 15.degree. 30.degree..