To obtain a resin composition that contains a (meth)acrylic ester of a specific polyester polyol and a photopolymerization initiator, and can provide an ultraviolet-curing ink composition which has excellent moisture-, grease- and water-proofness, and high washability.

This resin composition contains (A) a (meth)acrylic ester of a polyester polyol (A1) which is a reaction product of trimethylol octane (A1') with a polybasic acid (anhydride) (A1"), and (B) a photopolymerization initiator, such as 2,4-diethyl thioxanthone or benzophenone. The component A is obtained, for example, by a dehydration reaction of 1 equivalent of OH A1' with 0.01-0.7 equivalent of carboxyl group of A1" in an organic solvent serving as a dehydrating azeotropic agent at temperature of 90-200°C to produce A1, and then making 1 equivalent of OH A1 react with 0.9-3 equivalents of (meth)acrylic acid in the presence of a dehydrating azeotropic agent, an esterification catalyst and a polymerization inhibitor.