A method of edge-enhancing digital image data is provided, which includes: storing first and second image data; calculating difference between the first image data and the second image data; calculating a modification value by dividing the calculated difference value by a predetermined modification constant; comparing the difference with a predetermined value; and modifying the first and the second image data based on the modification value such that the first image data is decreased and the second image data is increased when the value of difference between the first and the second image data is lower than the predetermined value, and the first image data is increased and the second image data is decreased when the value of difference between the first and the second image data is higher than the predetermined value.