In a stereoscopic measurements on the aerial photogrammetric works, it is in general understood that the larger and the larger is a vertical scale exaggeration, the better and the better is height measuring precision. Despite the success with which a stereoscopic measurement has been applied to contour mapping as well as spot height measurement, no generally accepted theory for visual excess has yet been developed. This experiments aim at arrangement of a correlation between visual excess and height measuring precision. The stereoscopic measurements with parallax bar in the mirror stereoscope are carried out on the test model of which consists normal angle, wide angle and super wide angle respectively. With the result of this experiments, it is conclued that height measuring precision is proportional to the magnitude of visual excess.