An image processing method of making luminance correction on the basis of a luminance histogram showing luminance level distribution of image data expressing an image by a numerical value. A luminance average value, a luminance standard deviation, and a peak distance in the luminance histogram are obtained. A distribution discrimination value which can discriminate whether the luminance level distribution is deviated on the low/high luminance side in the histogram is compared with the peak distance. A halftone presence/absence discrimination value which can discriminate whether the luminance distribution is not deviated in the halftone in the luminance histogram is compared with the standard deviation. A backlight image is discriminated by the comparison results. An exposing state of an image other than a backlight image is discriminated by using an exposing state discrimination value. The proper luminance correction is made in accordance with the exposing state.