Provided are an electron beam curable resin composition including polymethylpentene, and a crosslinking agent, in which the crosslinking agent has a saturated or unsaturated ring structure, at least one atom among atoms forming at least one ring is bonded to any allylic substituent of an allyl group, a methallyl group, an allyl group through a linking group, and a methallyl group through a linking group, and a molecular weight is 1,000 or less, a resin frame for reflectors using the resin composition, a reflector, and a molding method using the resin composition.