To provide a resin composition for optical materials that has a low viscosity even if large quantities of zirconium oxide particles and an organic silicon compound are compounded therewith, can inhibit yellowing, and forms a resin having a high refractive index and exhibiting excellent transparency and heat resistance.

The resin composition for optical materials comprises zirconium oxide particles having an average particle size of 1-30 nm, a dispersant comprising a compound represented by formula (1), an organosilicon compound, and a compound having a polymerizable unsaturated group. In formula (1), R is a 3-24C alkyl and/or alkenyl group having a branched chain; AO is a 1-4C oxyalkylene group; n is a numerical value within the range of 3-30 expressing the average number of moles of alkylene oxide added; and X is a linking group comprising carbon, hydrogen and/or oxygen.