A resin composition comprising a fiber component and a resin component, whereinthe fiber component is (A) a surface-treated fiber (component A) which comprises 100 parts by weight of a fiber comprising a polyalkylene terephthalate and/or a polyalkylene naphthalene dicarboxylate (component Af) and 0.1 to 10 parts by weight of a sizing agent having a glass transition point of −80° C. or higher and lower than 70° C. and adhered to the surface of the fiber (component Ac); andthe resin component comprises (B) an ethylene-based copolymer containing a glycidyl group (component B), (C) a modified polyolefin resin modified with an unsaturated carboxylic acid and/or an unsaturated carboxylic acid derivative (component C), and (D) a polyolefin resin having a melt flow rate of 40 to 200 g/10 min (component D), except for the components C and D, the content of the component D being 30 to 850 parts by weight based on 100 parts by weight of the component A, and the total content of the components B and C being 5 to 630 parts by weight based on 100 parts by weight of the component A, and a molded article thereof.