PURPOSE: To simplify the processing method and to improve the accuracy of evaluation by making an illuminating system freely variable in three dimensions and irradiating the parts from an arbitrary angle.

CONSTITUTION: A support 16 and an illumination 17 are unified and moved in the vertical direction of a vertical direction straight gauge 14, and the illumination 17 is set to arbitrary height against parts 2. Also, the support 16 and the illumination 17 are unified and moved in the left and the right directions of a horizontal direction straight gauge 15. Moreover, by allowing the support 16 to execute a turning motion of right and left rotations, the illumination 17 is also subjected to right and left rotations. In such a way, by combining three forms of the vertical direction, the left and the right directions, and the left and the right rotation, the illumination 17 can make an arbitrary angle against the parts 2. As a result, in accordance with the parts 2, an optimal illumination angle can be set, and in many parts 2, an easily discriminatable recognition image is obtained, the processing method is simplified, and a result of evaluation can be obtained with high accuracy.