An active energy ray curable composition for coating an optical disk which comprises an urethane (meth)acrylate compound, an ethylenically unsaturated compound except said urethane (meth)acrylate compound and a photopolymerization catalyst; and an optical disk having a coating layer prepared by curing the composition. Also provided is an optical disk which comprises a substrate and, laminated thereon in the following order, a recording layer and a cured coating layer, wherein a recording light and/or a regenerating light enter from the surface of said cured coating layer side, characterized in that said cured coating layer is prepared by curing a curable composition exhibiting a curing shrinkage of 7.5 % or less, has a pencil hardness of 2B or harder, and exhibits a transmittance of a light having a wavelength ranging 380 to 800 nm of 75 % or more.