An image processing apparatus comprising: an acquisition means for acquiring a plurality of images including a reference image and a comparison image to be combined by combining corresponding pixels; a calculation means for calculating an edge amount of each pixel in the reference image to be combined with a corresponding pixel in the comparison image, the edge amount corresponding to a degree of an edge for the pixel; a determination means for determining composition weights of pixels in the comparison image with respect to a weight of corresponding pixels in the reference image when weighted averaging is performed, based on the edge amount of the corresponding pixels in the reference image calculated by the calculation means; and a composition means for combining (S207, S209) pixels of the reference image and of the comparison image by weighting corresponding pixels based on the composition weights determined by the determination means; characterized in that the determination means is adapted to determine, for each pixel in the comparison image to be combined with the corresponding pixel in the reference image, a composition weight with respect to the corresponding pixel in the reference image based on the edge amount of the corresponding pixel in the reference image such that: the composition weight for a first edge amount is lower than the composition weight for a second edge amount, wherein the second edge amount is smaller than the first edge amount (1 92), and the determined composition weight is, regardless of the edge amount of the reference image and an edge amount of the comparison image, equal or less than the composition weight of the corresponding pixel in the reference image for all pixels to be combined. an acquisition means for acquiring a plurality of images including a reference image and a comparison image to be combined by combining corresponding pixels; a calculation means for calculating an edge amount of each pixel in the reference image to be combined with a corresponding pixel in the comparison image, the edge amount corresponding to a degree of an edge for the pixel; a determination means for determining composition weights of pixels in the comparison image with respect to a weight of corresponding pixels in the reference image when weighted averaging is performed, based on the edge amount of the corresponding pixels in the reference image calculated by the calculation means; and a composition means for combining (S207, S209) pixels of the reference image and of the comparison image by weighting corresponding pixels based on the composition weights determined by the determination means; characterized in that the determination means is adapted to determine, for each pixel in the comparison image to be combined with the corresponding pixel in the reference image, a composition weight with respect to the corresponding pixel in the reference image based on the edge amount of the corresponding pixel in the reference image such that: the composition weight for a first edge amount is lower than the composition weight for a second edge amount, wherein the second edge amount is smaller than the first edge amount (1 92), and the determined composition weight is, regardless of the edge amount of the reference image and an edge amount of the comparison image, equal or less than the composition weight of the corresponding pixel in the reference image for all pixels to be combined. the composition weight for a first edge amount is lower than the composition weight for a second edge amount, wherein the second edge amount is smaller than the first edge amount (1 92), and the determined composition weight is, regardless of the edge amount of the reference image and an edge amount of the comparison image, equal or less than the composition weight of the corresponding pixel in the reference image for all pixels to be combined.