PURPOSE: To enable the obtaining of a tomographic section with a desk-top electronic calculator by connecting a plurality of linear data with varied density in the way of (j) lines to generate image data with varied density in a system of displaying section information of a specimen on a screen comprising j × i pixels.

CONSTITUTION: A CPU4 is provided to input a received signal of a probe 2 connected to an ultrasonic oscillator 3 and a distance signal and a reflection intensity signal are generated with a signal generator 20 thereof from a phase difference and intensity of an ultrasonic wave received to determine a total number of pixels valid among those in the (j) lines for one out of (i) columns with a totalizing circuit 21. Then, the pixels in the first line for the column involved are converted 22 to pixel data having varied density based on the total and the pixel data having varied density is grouped 23 with respect to the pixels in a plurality of columns out of (i) columns to generate linear data. A plurality of linear data with varied density obtained by moving the position of the probe 2 to a specimen are connected in the way of the (j) lines to generate 24 image data, which is shown on a display device 6.