An image checking process wherein only a defective or differential portion of a checked image is displayed together with its position and wherein no pre-processing is required for image positioning. A computer (3) captures a reference image or Fourier transformed image thereof from a storage part, a CCD camera (1) or a CCD camera (2) to acquire intensity information and phase information, and also captures an identified image or Fourier transformed image thereof from the storage part, CCD camera (1) or CCD camera (2) to acquire intensity information of the Fourier transformed image of the identified image. Then, the computer (3) determines the difference in intensity information between the reference image and the Fourier transformed image of the identified image and further determines an inverse Fourier transformed image of an expression obtained from the determined differential intensity information and the phase information of the reference image to output the inverse Fourier transformed image to an output part or display part. The inverse Fourier transformed image is used to extract, as a difference between the identified image and the reference image, an image defect of the identified image or the image difference between the identified image and the reference image.