Laser robot can weld more accurate than Arc welding. However, the accuracy of positional match is demanded. Then, the system the welding robot is equipped with the camera and slit beam irradiating to the welding object is assumed. And, the irradiated appearance is photographed. By giving geometrical analysis to the obtained beam image, laser robot is controlled. Here, as the preparation stage, about linear regression of beam for geometrical analysis is described.