In an optical storage, a base is defined in a bottom of a space which receives a disk. A drive unit is mounted on the base for turning the disk around a drive axis. A shroud is defined in a side of the space, and a cover is defined in a top of the space. The cover has a slanted line extended from a central portion of the cover toward the shroud at an upward inclination with respect to a disk plane when seen in a cross-section taken along a line perpendicular to the disk plane.