The tomographic testing apparatus employs two data collection modes. One of these modes is a reference data collection mode in which almost all of the prescribed image data of a reference sample is obtained. The reference sample has no defect. The other of these modes is a measurement mode in which a predetermined small number of image data of an inspection sample is obtained. The inspection sample to be tested may have defective portions. The tomographic image of the inspection sample is obtained from the combination of the inspection sample image data and the reference sample image data from which specific data corresponding to the inspection sample image data is deleted.