The present invention relates to a process for preparing a vinyl chloride copolymer resin by copolymerizing a vinyl chloride type monomer and a macromonomer having a polymer comprising an ethylenically unsaturated monomer containing a double bond in a main chain, which generates only a few scales and shows excellent polymerization stability. The present invention is achieved by the process for preparing a vinyl chloride copolymer resin by copolymerizing a vinyl chloride type monomer and a macromonomer having a polymer comprising an ethylenically unsaturated monomer containing a double bond in a main chain, wherein the vinyl chloride type monomer and the macromonomer having a polymer comprising an ethylenically unsaturated monomer containing a double bond in a main chain are dispersed and mixed at a temperature from 20.degree. C. to 60.degree. C. for at least 1 minute, and then copolymerization reaction thereof is initiated.