The image processing apparatus includes: an input unit configured to receive input of a plurality of images; an alignment unit configured to select each of the plurality of images one by one as a base image, and aligns the base image and each of comparison images; a selection unit configured to select the comparison image to be combined with the base image from among the comparison images aligned with the base image for each of the base images, calculate a common region in which images included in the combination can be commonly drawn, and select the combination in which the ratio of the common region to the base image satisfies a predetermined condition; a determination unit configured to determine the combination that maximizes the number of comparison images from the selected combination; and an output unit configured to output an image group corresponding to the determined combination.