Provided is a resin composition for sealing LED elements, including (i) an organopolysiloxane with a polystyrene equivalent weight average molecular weight of at least 5×103, represented by an average composition formula (1): R1a(OX)bSiO(4-a-b)/2, in which, each R1 represents, independently, an alkyl group, alkenyl group or aryl group of 1 to 6 carbon atoms, each X represents, independently, a hydrogen atom, or an alkyl group, alkenyl group, alkoxyalkyl group or acyl group of 1 to 6 carbon atoms, a represents a number within a range from 1.05 to 1.5, b represents a number that satisfies 0<b<2, and 1.05<a+b<2), and (ii) a condensation catalyst. Also provided are a cured product produced by curing the composition and a process for sealing LED elements with the cured product. The composition exhibits excellent thermal resistance, ultraviolet light resistance, optical transparency, toughness and adhesion.