An optical proximity effect correcting method in a semiconductor manufacturing process includes adding, detecting, judging, and deleting. The adding includes adding a first correcting region around a portion of a first design pattern. The portion faces a second design pattern. A first corrected design pattern includes the first correcting region and the first design pattern. The detecting includes detecting a space between the first corrected design pattern and the second design pattern. The judging includes judging whether the space is smaller than or equal to a predetermined value. The deleting includes deleting at least a portion of the first correcting region such that the space is larger than the predetermined value, when the space is smaller than or equal to the predetermined value.