To permit a doctor to make medical examination while he has conversation with the patient by making region specification for a certain part of the image of a subject given on a monitor for inspection, displaying the specified region in superposition over the image of the subject, distinguishing the image before movement when the subject has moved, and moving the specified region to the position where the image of the subject has moved.

A doctor observes the figure of his patient given on a display device 38, and the contour of the infected zone is traced by a light pen 42. Thereby the figure of the selected region is displayed in superposition over the infected zone on the screen. If the patient moves in this condition, the selected region separates from the image. At this time, the position of the infected zone accommodated in the region at all times is recognized and pursued, and the selected region and the patient are moved simultaneously. That is, a correlation calculation part 35 compares at certain intervals the change of the display in the same position about the previous screen and the current screen. The correlational calculation of the picture element is made depending upon the result from comparison, and the motions of the previous and the current screens are calculated quantitatively, and the region is moved and superposed on the image.