Abstract: Height gradient values change around their boundary pixels significantly since buildings in built-up areas are often higher than the surroundings. A Stereo Pair Disparity Index(SPDI) image is produced from the disparity image generated from epipolar images of a stereo pair. Built-up area results in an epipolar image are obtained by executing spatial clustering on pixels with high values in the SPDI image, and can be located in the raw image of a stereo pair. However, built-up area results that are separately detected from two images are inconsistent, and cannot be aligned because of the disparity between the homonymous points. To address this problem., the generated disparity images were aligned and overlayed to achieve reliable, consistent results. Experimental results show that built-up areas were identified from two stereo pairs accurately through our method.