Abstract: The liquid detergent composition of the invention comprises a halogenated hydrocarbon solvent, e.g. methylene chloride, an anionic and/or non-ionic surface active agents, a quaternary ammonium hydroxide, e.g. tetramethyl ammonium hydroxide and choline, and, optionally, a lower aliphatic alcohol, e.g. methyl alcohol, each in a limited proportion. The detergent composition is very effective in the cleaning works of articles of a transparent plastic resin, e.g. polycarbonate resin, and metal or glass molds for the preparation of such resin articles by casting polymerization, of which uppermost cleanness on the surface is very essential in respect of oily, greasy and resinous contaminants.