An image processing system produces highly accurate determination of a local area that does not conform to an assumed change. Positional displacement amount calculation element 91 calculates a positional displacement amount between a target image and a reference image. Pixel operation element 95 relates a pixel in the target image to a pixel in the reference image by specifying the pixel in the reference image nearest a position of the pixel in the target image when the target image is corrected so as to resolve the positional displacement, calculates a relative pixel differential vector which is a differential vector of respective vectors of the relative pixels, and determines whether or not the pixel in the target image is a pixel of the local area, based on the relative pixel differential vector and an ellipsoid in a predetermined space, the ellipsoid relating to the pixel in the reference image.