Abstract: In the present invention, the difference between regions in which the signal value ranges are close to each other or the presence of overlapping regions of signal values can be clearly displayed on a predetermined image region of an observation image, and the displayed regions and display state thereof can be easily adjusted based on the signal value ranges. The present invention is configured such that a plurality of separate and mutually independent display property curves can be set on the same coordinate system, and a color and a degree of opaqueness, which are established by any number of display property curves from among the plurality of display property curves that are set, can be at once reflected in the image within the region to be observed.