An industrial machine has a main unit 14, a working implement 8 installed on the main unit, and two cameras 18 and 19 each mounted at a known position with respect to a machine center of the main unit. At least three targets 21 are installed on the working implement so that the targets are within visual field of each of the two cameras. An arithmetic processing device 23 extracts the images of at least three targets in common to the images from stereo-images taken by the two cameras, for obtaining a three-dimensional position of each target image, and for calculating a position and a posture of the implement with respect to the industrial machine main unit based on the three-dimensional position obtained.
