1. An image processing device that combines a plurality of color filter array images obtained by shooting a same subject, the image processing device comprising: a displacement amount calculation portion configured to calculate a displacement amount of a reference image with respect to a standard image, wherein among the color filter array images, one image is the standard image, and an image different from the one image is the reference image; and a synthesis processing portion configured to perform synthesis processing based on the displacement amount calculated by the displacement amount calculation portion, according to pixel values of a standard image pixel and a reference image pixel that are corresponding pixels at corresponding pixel positions between the standard image and the reference image, so as to generate a synthetic color filter array image, wherein, when colors of the corresponding pixels differ between the standard image pixel and the reference image pixel, the synthesis processing portion generates, from the reference image, a pixel value of a same color as a color of the standard image pixel by interpolation processing, and performs the synthesis processing according to the pixel value generated by the interpolation processing and the pixel value of the standard image pixel.