A resin composition for an optical material that has excellent balance of refractive index of resin, Abbe number, heat resistance, specific gravity, and resin strength, a resin obtained by curing the resin composition, and an optical material are provided.A polymerizable composition comprising the following is used: An alicyclic isocyanate compound represented by the formula (1) and/or the formula (2):  (In the formula (1), n represents integer of 0 to 3)  and (a) at least one compound of the polythiol compound having at least two thiol groups in one molecule and/or the polythiol compound having at least two thiol groups and at least one (poly)sulfide bond other than the thiol group in one molecule, and (b) at least one compound of the polyhydroxy compound having at least two hydroxy groups in one molecule and/or the (poly)hydroxy(poly)mercapto compound having at least one hydroxy group and at least one thiol group.