An optical proximity correction (OPC) processing method may include at least one of the following steps: Detecting coordinate values of individual piece patterns constituting a graphic design system (GDS). Merging to the form of a specific pattern, composed of outermost coordinate values, on the basis of the detected coordinate values. Shrinking the merged GDS pattern and forming a GDS pattern having a desired magnifying power. Performing an optical proximity correction (OPC) process on the GDS pattern having the desired magnifying power.