A coating composition capable of yielding a cured product having a high refractive index comprises fine particles of at least one oxide selected from the group consisting of iron oxide, titanium oxide, cerium oxide, zirconium oxide, antimony oxide, zinc oxide and tin oxide, and composite oxides thereof, an epoxy group-containing silicon compound or a partial hydrolyzate thereof, and an organic compound having one OH group or SH group in the molecule and containing in the main chain thereof at least one bonding unit selected from the group consisting of --O--, --CO--O--, --S--, --CO--S-- and --CS--S-- along with at least one unsaturated group, the organic compound being soluble in water or a lower alcohol having up to 4 carbon atoms. When cured on a high refractive index substrate, the composition yields a cured product which has a very high hardness and is able to be deep dyed while suppressing development of interference fringes. Coated articles including coated plastic lenses having the cured film of the composition are also provided.