PURPOSE: To discriminate the back and the front face of a part whose back and front faces are hard to be discriminated rapidly and supply those parts with both faces discriminated.

CONSTITUTION: A part 31 is taken out from a part supplying part by a robot 4 without discriminating its back face and the front face and then a designated position of the part 31 is irradiated by laser beam by a laser beam radiating part 2. The back and front faces of the part 31 are discriminated by examining if the reflected light is detected at a light detecting part 3 and the part 31 is moved to a designated part mounting position only when it is in front face state.