To gather a rock, it is necessary how to get information of the surface around a sample. Usually, a surface information is brought by a special sensor such as Laser Range Finder and Stereo Camera. These sensors, however, needs more weight and power consumption and are used for only one function such as the surface measurement. And furthermore, there are some difficulties to use those sensors in some case. In this research, we propose Shadow Range Finder: SRF, which can make good use of a shadow for the measurement of a surface information under the direct sunlight. Shadow is strong for above mentioned problem, and would be recognized in the case of a halation. The measurement by SRF uses a single camera, which should be installed on a manipulator for a sampling, and a link of a manipulator, which produce its shadow. The principle of SRF is same as Laser Range Finder, and a shadow is used for scanning slit instead of a laser. In this paper, experimental results of actual objects is shown, and we discusses about accuracy of measurement data. Finally, we evaluate image thresholding method by the consideration of theoretical value at a circular light source.