Abstract: A novel aroyl ketone derivative represented by formula (I) is disclosed:Ar(COCH.sub.2 COR.sup.1).sub.n (I)wherein R.sup.1 represents a saturated or unsaturated hydrocarbon group having 1-24 carbon atoms, or a linear or branched alkoxyalkyl or alkenyloxyalkyl group having 1-24 carbon atoms, dialkylamino group having 1-24 carbon atoms, Ar represents a benzene or naphthalene ring which may be substituted with one or more hydroxyl groups, alkoxy groups having 1-24 carbon atoms, alkenyloxy groups having 1-24 carbon atoms, polyoxyleneoxy groups, or .alpha.-methylenedioxy groups, and n denotes an integer of 1-4. An UV-ray absorber and cosmetic composition comprising the aroyl ketone derivative of formula (I) are also disclosed. Aroyl ketone derivative (I) of the present invention can provide an excellent UV-ray absorbing effect and has outstanding stability against light, and the UV-ray absorber or cosmetic composition containing the aroyl ketone derivative (I) can exhibit an excellent sunscreening effect.