To obtain a quick-curing resin composition capable of sufficiently exerting inherent air curability of a dicyclopentenyl group-having resin composition and coloring little after being cured.

The radical curable resin composition comprises a terpolymer (C) and a monomer (D) copolymerizable with (C) component, wherein the terpolymer (C) is obtained by reacting, at a specific ratio, a reaction product (A) of a specific ratio of dicyclopentadiene and maleic acid with an epoxy resin (B) having ≥2 epoxy groups. Another radical curable resin composition comprises 100 pts.wt. (meth)acrylic syrup composition (E), 5-150 pts.wt. e.g. a specific terpolymer (G) obtained by reacting the reaction product of dicyclopentadiene and maleic acid with (B) component and, if necessary, 5-50 pts.wt. of e.g. a vinyl ester resin (I).