There are provided a light penetration depth evaluation method capable of evaluating the penetration depth of ultraviolet light for a measurement target in a non-destructive and non-invasive manner, a performance test method using the evaluation method, and an optical tomography apparatus using the evaluation method. Using an optical tomography method of splitting low coherent light (L 0 ) into sample light (L 1 ) and reference light (L 2 ), emitting the sample light (L 1 ) to a measurement target (S) in a line shape, generating interference light (L 4 ) by superimposing reflected light (L 3 ) from the measurement target (S) due to emission of the sample light (L 1 ) and the reference light (L 2 ) on each other, and acquiring a two-dimensional spectroscopic tomographic image of the measurement target (S) by spectroscopically detecting the interference light (L 4 ) and performing frequency analysis, an arbitrary wavelength region in an ultraviolet region is cut out from low coherent light including a wavelength region from an ultraviolet region to a visible region and the arbitrary wavelength region is shaped into a spectrum having an arbitrary wavelength width, the two-dimensional spectroscopic tomographic image is acquired as using the low coherent light (L 0 ), and the penetration depth of the sample light for the measurement target is evaluated based on the two-dimensional spectroscopic tomographic image.
