An optical disk apparatus includes an objective lens system for producing a beam
spot on an optical disk, a slider movable relative to the optical disk, and a fine
tracking mechanism for shifting the beam spot in a radial direction of the optical
disk. The objective lens system is composed of a first lens and a second lens.
The second lens is held by the slider and disposed closer to the optical disk than
the first lens is. The tracking mechanism shifts the second lens in the radial
direction of the optical disk for tracking control.