Image quality of tomographic images obtained by optical tomographic measurement is improved. Spatial frequency processes are administered on a tomographic image, with the frequency processing properties (high frequency gain) in the scanning direction of a measuring light beam set to be lower than the frequency processing properties (high frequency gain) in the direction of the optical axis of the measuring light beam. For example, a smoothing process that removes high frequency components is administered to the tomographic image only in the scanning direction. Alternatively, a sharpening process that emphasizes high frequency components is administered to the tomographic image only in the direction of the optical axis. As a further alternative, a smoothing process that removes high frequency components is administered to the tomographic image in the scanning direction, then a sharpening process that emphasizes high frequency components is administered to the tomographic image in the direction of the optical axis.