The landform changes in the natural monument area of Tottori Sand Dune are analyzed by image processing of the aerial photographs taken by the Geographical Survey Institute (GSI), JAPAN in 1970, 1981 and 1990. Neither ridges nor bottom parts of the sand dunes shown on the photographs are clear enough to allow the specification of the landforms. The most identifiable parts are slip faces of the dunes where slope angles are almost constantly 35 degrees. They can be easily identified from the other parts based on the brightness of the images. Using this difference in the brightness, the slip faces were classified and mapped with different colors after the geometric correction. Then the movements of the dunes were analyzed by overlaying the images. By this procedure, the movements of slip face could be easily identified and measured. The contour maps published by GSI and Tottori Prefecture were used to verify the data of the abovementioned procedure. The results show that aerial photographs provide useful information about sand dune movements with sufficient accuracy.