PURPOSE: To easily make possible the grasp of the general trend of the fractionation and discrimination of mutually neared echoes and the azimuth of the echoes by widening the central neighborhood of a circular display part indicating the whole of a search range to display circularly outside.

CONSTITUTION: A doughnut-shaped display 3 is provided at the outside of a normal display 1. When a search range is made R, the display range of the display 1 is from the distance zero to R and the distance of zero to Rd (Rd is indicated, for instance, as 0.5R) in the range of the display 3 is shown on a dotted line as the range 2 in the display 1. And the position where the distance 2 exceeds the range 2, namely, an echo 6 at a great distance is not overlooked because it is shown in the display 1 as it is. Because echoes 4, 5 are shown in the display 3 in addition to the display 1 at short distances and they can be easily separated in the display 3 even if the echoes are two mutually near to separate.