To provide an optical resin composition containing carbonate crystals, which have oriented birefringence, have a needle- or rod-like shape, and are able to negate the birefringence without sacrificing the light transmittance of a transparent polymeric resin where the carbonate crystal exists, and a method for producing the resin composition. To achieve this provided are an optical resin composition containing a resin and carbonate crystals, wherein the carbonate crystals have a specific surface area of 4 m.sup.2/g or more, and the carbonate crystals dispersed into the resin have an average dispersion diameter of 500 nm at a maximum, and a method for producing the optical resin composition.