Disclosed are an optical waveguide that comprises (A) a copolyester carbonate having aliphatic segment(s), and a method for producing it; and an optical waveguide made from a polycarbonate resin composition that comprises (A) a copolyester carbonate having aliphatic segment(s) and (B) an aromatic polycarbonate, and a method for producing it. The polycarbonate resin composition for the optical waveguide has the advantages of high mechanical strength and improved flowability.