The present invention provides a resin composition that includes (A) a polymer compound that has, on a side chain of a main chain polymer, through a linkage group containing a hydrogen-bonding group and a ring structure, a terminal ethylenic unsaturated bond, and is soluble or swelling in water or an alkali aqueous solution, and (B) a compound that generates radicals when exposed to light or heat. The invention further provides a thermo/photosensitive composition that includes (A') a polymer compound that has a non-acidic hydrogen-bonding group on a side chain and is soluble or swelling in water or an alkali aqueous solution, and (B') a compound that generates radicals when exposed to light or heat.