Aiming to treat the area close to the boundary between tumors and normal brain tissue in neurosurgery, a computer controlled robotic laser surgery system with volume mapping function has been developed. In order to make sure the location of residual tumors, it is important to show the volume data of MR image to surgeon for designating the target area to be irradiated by laser on the computer monitor screen. The improved system has performed the volume data display as a 2-dimentional outline that is appeared by crossing the target surface imposing to the surface image from CCD camera. This newly system also has the function of surface shape measuring by using the auto-focus mechanism and plotting the data on the monitor screen. On our evaluation, less than 0.5mm depth resolution can be obtained in sensing target surface by this system.