An apparatus for optical proximity correction according to an embodiment of the present invention has a data collector configured to collect source data of a circuit pattern, an edge line detector configured to detect edge lines each of which has a size that is less than a line width of the electrical circuit pattern, an edge line modifier configured to modify each of the edge lines so as to prevent an excess optical proximity correction, and a data synthesizer configured to generate pre-correction data from the modified edge lines and the source data.