PURPOSE: To prevent the invasion of dust not only for a movable part but also for a fixed part by providing a cover, which seals the fixed part and the movable part, and a slide cover to be interlocked with the move of the movable part.

CONSTITUTION: An optical head is constituted so as to make a light flux 6, which is emitted from an emissive port 10 of a fixed optics S, incident from an incident port 11 to a movable optics M, to pass the light flux through an objective lens 5, to form a spot on an optical disk 9 and to return reflected light from the disk 9 to the optics S reversely along the above mentioned route. For a cover 1, a minimum long hole 8 is provided so that a fine actuator 4 can be moved in all the recording areas of the disk 9, and the optics S and M are covered with this cover 1. A slide cover 7 can be moved on the cover 1 while being interlocked with the move of the optics M, and provided in a size so as to cover the hole 8. Thus, the dust is not stuck to an optical path excepting for the surface of the lens 5.