An optical disk of a system wherein a recording layer is to be irradiated with a laser beam through a thin film cover layer, wherein on the surface of the thin film cover layer, a hard coat layer is formed which is made of a cured product of an active energy ray curable composition comprising a polymerizable monomer (A), a colloidal silica (B), a lubricity-imparting agent (C) and an active energy ray polymerization initiator (D), as components. The lubricity-imparting agent (C) contains a lubricity-imparting agent (C-T) having, in one molecule, a moiety (c-1) exerting lubricity, a moiety (c-2) excellent in compatibility with the polymerizable monomer and an active energy ray curable functional group (c-3). In the optical disk of the present invention, the hard coat layer formed on the surface of the thin film cover layer is excellent in abrasion resistance, transparency and long-term surface lubricity.