An optical disk player, used for reproducing data recorded on a laser or compact disk, is disclosed. In the disk player, a dust cover is rotatably hinged to the top surface of a pick-up unit. The above dust cover is brought into movable contact with and is operated in conjunction with the guide surface of a cam member. The dust cover thus selectively covers or opens the objective lens of the pick-up unit. Due to the dust cover, it is possible to almost completely prevent foreign substances, such as dust, from sticking on the lens, thereby effectively protecting the lens. The dust cover precisely opens or covers the lens in conjunction with a slidable movement of a guide rod of the dust cover relative to a sectioned guide surface of the cam member. The guide surface of the cam member is formed within a range corresponding to a distance between the inside edge of the chucking place of the disk to the junction between the chucking place and the data place of the disk. The optical disk player is thus free from any operational error and has an improved operational reliability.