1. A method for brightness equalization of a plurality of images, the method comprising: receiving at least two input images; composing the at least two input images into a single composite image; setting a correction area corresponding to each input image in the composite image, and calculating a brightness histogram of each correction area; calculating a representative value of at least one modal in the brightness histogram, and grouping a modal of each correction area based on the representative value; calculating a correction target value of each group based on a representative value of modals grouped into each group; calculating a corrected value by subtracting the representative value of modals of each group of each correction area from the correction target value of each group; and correcting brightness by adding the corrected value to a pixel value of each group of each correction area.