An object of the present invention is to provide a radiation-curable coating material which forms a cured coating film having high hardness and low curing shrinkage, a radiation-curable resin composition for obtaining the radiation-curable coating material, and a method for forming a protective layer using the radiation-curable coating material. The present invention provides a radiation-curable resin composition including an urethane (meth)acrylate (A), which is obtained by reacting a bicyclo ring-containing polyisocyanate compound (a1), a hydroxyl group-containing, trifunctional or higher polyfunctional (meth)acrylate (a2) and a tris(2-hydroxyalkyl)isocyanurate di(meth)acrylate (a3); a radiation-curable coating material including the above resin composition; and a method for forming a protective layer, which includes: applying the above radiation-curable coating material onto a support to form a layer of the radiation-curable coating material thereon; and irradiating the layer of the coating material with radiation thereby curing the layer of the coating material to form a protective layer.