PURPOSE: To easily remove a background part by forming a digital video signal obtained from a video signal into a histogram data, removing the signal of the background part from the digital video signal by a look-up table and calculating the center of gravity for a target in a target area.

CONSTITUTION: The digital video signal obtained from the video signal outputted from an image pickup camera 1 is formed into the histogram data by a histogram processing circuit 8, and a work data obtained by working this histogram data is transferred to a look-up table 19. In this look-up table 19, the signal of the background part is removed from the digital video signal, and the center of gravity for the target in the target area is calculated. Thus, even when the density distribution of the background part is complicated, the target can be segmented.