The welding is the important basic technology of joining two materials together. The quality is influenced in the skill of the personwho carried out the welding. Therefore, the welding license examination and the welding skill contest are carried out in each prefecture. The judge checks the height and width of the welding bead by using caliper whether it has satisfied the standard value. In addition, the beauty is evaluated and the score is decided by the visual observation. Therefore if the judge is different, it is different in the decision for the same weld bead. In this paper, the authors propose a system of quantitative evaluation of the welding bead by using three-dimensional data obtained by the slit light projecting method.