Abstract: There is provided a disk apparatus having a construction in which a reproducing unit is accommodated inside an enclosed space, whereby an optical head is protected from external dust. The optical head reads information recorded on a disk. Component parts of the disk apparatus are accommodated inside a case. The optical head is provided on a chassis formed in a box-like shape, the chassis having walls with ends which have contacting surfaces which come in contact with the case. A circuit board assembly which receives circuit processing information from the optical head is positioned outside the chassis. The chassis and the case together form an enclosed space, the optical head being accommodated inside the enclosed space.