To provide a thermoset highly refractive resin composition providing a cured product having excellent heat resistance, adhesiveness, hardness, solvent resistance and transparency, exhibiting good coatability and suitable for a clear coating agent for an optical article.

The resin composition contains a copolymer, a melamine-based compound or guanamine-based compound, and an organic solvent. The copolymer is obtained by copolymerizing a monofunctional (meth)acrylate compound having a specific structure with a biphenyl skeleton, a monofunctional (meth)acrylate compound having one hydroxy group in the structure, and a silicon-containing monofunctional (meth)acrylate compound.