To enhance the degree of discrimination of the presence of the flaw in a semiconductor chip upon inspection using an ultrasonic imaging apparatus.

Gates are set at two or more places before and behind a flaw part to inspect the signal amplitude or signal integrated value ratio in the gates, and this signal ratio is compared with the reference data at a normal part to exhibit the presence of a flaw or spatial distribution as an image. The compared value of this echo signal ratio and the echo signal ratio at the normal part is displayed as a two-dimensional image to visually exhibit the distribution of the flaw as an image. The degree of discrimination of the signals between both cases that the flaw is present and that flaw is absent is enhanced to enhance the precision of a flaw distribution image. Further, a change in the signals in both cases that an ultrasonic beam is accurately superposed on a flaw position and not accurately superposed on the flaw position becomes larger with the enhancement of a discrimination ratio, thereby space resolution in an orientation direction is enhanced.