An optical coherence tomography apparatus configured to divide light output from a light source unit into signal light and reference light, detect interference light obtained by superimposing the signal light having passed through an object onto the reference light, and form a tomographic image of the object based on the detection result, characterized in that the optical coherence tomography apparatus further comprises: - a storage part configured to previously store relation information in which a representative wavelength, a wavelength range including this representative wavelength, and a light loss amount due to absorption by a medium are related to each other; - a display configured to display the relation information which is distribution information of the light loss amount due to absorption by the medium wherein the distribution of the light loss amount is indicated by contour lines in a space spanned by a first coordinate axis indicating the representative wavelength and a second coordinate axis indicating the wavelength range including said representative wavelength; - a pointing device for designating coordinates positioned within a region whose border is a contour line indicating a predetermined light loss amount within the displayed distribution information; and that said light source unit is configured to output light with the wavelength range including the representative wavelength corresponding to the designated coordinates. characterized in that the optical coherence tomography apparatus further comprises: - a storage part configured to previously store relation information in which a representative wavelength, a wavelength range including this representative wavelength, and a light loss amount due to absorption by a medium are related to each other; - a display configured to display the relation information which is distribution information of the light loss amount due to absorption by the medium wherein the distribution of the light loss amount is indicated by contour lines in a space spanned by a first coordinate axis indicating the representative wavelength and a second coordinate axis indicating the wavelength range including said representative wavelength; - a pointing device for designating coordinates positioned within a region whose border is a contour line indicating a predetermined light loss amount within the displayed distribution information; and - a storage part configured to previously store relation information in which a representative wavelength, a wavelength range including this representative wavelength, and a light loss amount due to absorption by a medium are related to each other; - a display configured to display the relation information which is distribution information of the light loss amount due to absorption by the medium wherein the distribution of the light loss amount is indicated by contour lines in a space spanned by a first coordinate axis indicating the representative wavelength and a second coordinate axis indicating the wavelength range including said representative wavelength; - a pointing device for designating coordinates positioned within a region whose border is a contour line indicating a predetermined light loss amount within the displayed distribution information; and that said light source unit is configured to output light with the wavelength range including the representative wavelength corresponding to the designated coordinates. <EOS>