To highly accurately detect a position of a moving body within a move area by detecting a corresponding light-emitting unit on the basis of image information of the photographed moving body and a color pattern of a projected light of a each light-emitting unit which is stored beforehand.

Light-emitting units 3A-3J are arranged outside a work area of a robot along one side 2A of the work area. The work area is illuminated by a projected light from each light-emitting unit. The robot photographs by a camera 20 the projected light of the front light-emitting unit in an X direction. Pixels of each color component included in an obtained image signal S1 are extracted at color extraction parts 31A-31Z. A color pattern of the projected light of the light-emitting unit 3A-3J corresponding to an output of each extraction part is detected on the basis of the output of the extraction part. The corresponding light-emitting unit is detected from the detection result and color patterns of the light-emitting units 3A-3J stored beforehand at 34. A position of the robot at the time is detected from the detection result and position information of each light-emitting unit 3A-3J stored at 35.