A change discrimination device capable of discriminating an alteration of a photographing target only from an aerial photograph or irrespectively of a difference in lighting conditions or photographing conditions at the time of taking a photo, and at minute distance intervals on a pixel basis, which receives input of a plurality of aerial image data at a new time point and an old time point, generates three-dimensional data (DSM) by subjecting the applied aerial image data to stereo-matching processing, generates ortho-image data and ortho-DSM data by normalizing the aerial image data and the generated DSM data, compares colors by using the generated ortho-image of the new time point and ortho-image of the old time point and compares heights by using the generated ortho-DSM data of the new time point and ortho-DSM data of the old time point to discriminate an alteration of a feature on the earth.