Abstract: The present invention relates to a phenoxy resin for an optical material obtained by subjecting at least one selected from specific difunctional epoxy resins and at least one selected from specific difunctional phenols to polyaddition reaction, wherein a film comprising the above phenoxy resin has a refractive index of 1.580 or less at 25° C. and a wavelength of 830 nm, a resin composition for an optical material containing the above phenoxy resin, a resin film for an optical material comprising the above resin composition and an optical waveguide produced by using the above resin composition and/or the above resin film.