PURPOSE: To obtain distribution of reflection intensity of an object to be measured by performing deconvolution for a series of beam intensity for each specified orientation angle and for a series of intensity of reception signal for each specified orientation angle.

CONSTITUTION: A reception signal 200 is stored in a memory circuit 16 through a pulse width processing circuit 12 etc. Also, angle signal is supplied to a beam pattern memory circuit 24 from a scanning angle control circuit 18. Then, H-row (series with an intensity of signal 200) signals H0 - Hm which are output from a read-out circuit 22 from a circuit 16 and S-row (series of beam intensity) signals S0 - Sn output from the circuit 24 are subjected to deconvolution by a deconvolution circuit 26. Namely, the H and S rows are expressed by a high- order expression of x and distribution of reflection intensity of the object to be measured is obtained from each term where x of quotient of division of both is equal to 1. Then, it is performed along scanning direction for a same distance in sequence. The obtained reflection intensity distribution is displayed in a display 28.