This invention provides an image processing apparatus including a unit which generates index image data, a unit which obtains a position of thumbnail image data in the index image data, a unit which divides the index image data so as to prevent overlap of the thumbnail image data, a unit which calculates a histogram of a luminance value of image data corresponding to each partial area including the thumbnail image data, a unit which determines image correction characteristics of each piece of image data based on the histogram and performing image correction, and a unit which reconfiguring the index image data using the corrected image data to output the reconfigured index image data.