A cleaning instrument which can easily clean a lens in a short time without damaging the lens, which can clean both side surfaces of the lens at the same time, and which can serve also as a case for storing the lenses, includes a cleaning ball for cleaning a lens. A cleaning vessel is formed with a recessed cleaning chamber for housing a contact lens and the cleaning ball. The cleaning chamber has a bottom concave inner surface which is curved complementarily to the curvature of the lens so that the lens can be mounted in face-to-face contact therebetween.