PURPOSE: To prevent a person to be measured from being injured by directing optical axes of TV cameras mounted on two two-axis racks to the target through an image tracking device and a servo driving means, and calculating the position from attitude signals from the racks.

CONSTITUTION: Video signals 6 which include the target which are outputted from the TV cameras 1a and 1b are inputted to the image tracking device 3 to perform digital image processing measurement, and a tracking error signal 7 proportional to the extent of the position shift from the center of a screen is outputted to a servo amplifier 5. The amplifier 5 drives the two-axis racks 2a and 2b to direct the optical axes of the cameras 1a and 1b to the target. Further, the racks 2a and 2b output rack attitude signals 8a and 8b which indicate the elevation and swivel direction. An arithmetic unit 9 uses the signals 8a and 8b and coordinate signals of the racks 2a and 2b to calculate the three-dimensional position of the target from a specific relational expression, and outputs the result to a display device 10 and a recording device 11.