To make it possible to reduce cost of processing and to heighten the beautifulness of appearance and flame polishability by subjecting a resin molding comprising a specified methyl methacrylate copolymer to a special processing.

A copolymer of a major proportion of methyl methacrylate with a minor proportion of an acrylic ester (e.g. methyl acrylate, ethyl acrylate or n-propyl acrylate) is provided. A methyl methacrylate monomer mixture containing 2-14mol% acrylic ester or a polymer/monomer mixture containing 30wt.% or below its copolymer and a monomer is cast-polymerized in the presence of a polymerization initiator to obtain a resin molding comprising a methyl methacrylate copolymer having a glass transition temperature of 90°C or above. This molding is flame-polished with an oxygen/hydrogen flame burner so that at most 50/mm2 blisters having a diameter of 10μm or above may be left on the flame-polished surface when a cross section of this molding is flame-polished.