PURPOSE: To accurately discriminate the distance of objective matter according to a color by forming mixed color data by setting receiving intensity and a distance to parameters.

CONSTITUTION: The receiving data S2 obtained by converting the ultrasonic reflected wave from objective matter to an electric signal is stored in a receiving data memory 11 and a signal processor 10 calculates a dip 10a, an azimuth 10b and a distance 10c with respect to the objective matter. A beam forming operation circuit 12 performs the beam forming operation of the receiving data S2 to calculate receiving intensity 12a and this receiving intensity 12 and the distance 10c are used as parameters to form mixed color data and a front image is colored by this mixed color data to be displayed on a CRT 1. Therefore, even when the reflectivity of an ultrasonic wave is different according to the objective matter, the difference of reflectivity is corrected on the basis of a distance to make it possible to properly discriminate a distance.