An image acquisition unit acquires multiple image data sets of pixels in array, having subject distortion due to focal plane shutter effects, corresponding to images taken at continuous exposure timings; a coefficient storage unit stores coefficients, determined by which number-in-order of multiple images that the image data set corresponds to, and by each pixel position in the image; a multiplying unit multiplies a pixel value of a predetermined pixel in the image data sets, by the coefficient stored in the coefficient storage means; and an adding unit adds each pixel value of a predetermined number of the image data sets. The coefficients include a coefficient wherein, at the earliest image data set, pixels exposed earlier are weighted less and pixels exposed later are weighted more, and a coefficient wherein, at the latest image data set, pixels exposed earlier are weighted more and pixels exposed later are weighted less.