A resin composition for an optical waveguide is provided, which has excellent adhesiveness to a cladding layer of the optical waveguide and excellent patternability for formation of a core portion of the optical waveguide and reduces the optical waveguide loss. An optical waveguide produced by using the resin composition is also provided. The resin composition comprises: (A) a multifunctional partially-acrylated epoxy resin, as a major component, having an epoxy group and a (meth)acrylate group in the same main chain thereof; and (B) a photopolymerization initiator as a curing component. The optical waveguide includes: a substrate; a cladding layer provided on the substrate; and a core portion provided on the cladding layer for transmission of an optical signal; wherein the core portion is formed from the resin composition.