The present invention provides a crystalline quality evaluation apparatus (1) and a crystalline quality evaluation method for thin-film semiconductors, which are designed to evaluate crystalline quality of a sample (2) of a thin-film semiconductor (2a) by emitting excitation light and an electromagnetic wave to irradiate a measurement site of the sample (2), and detecting an intensity of a reflected electromagnetic wave from the sample (2). In the present invention, the thin-film semiconductor (2a) of the sample (2) is formed on an electrically conductive film (2b), and a dielectric (3) transparent to the excitation light is additionally disposed between the sample (2) and a waveguide (13) for emitting the electromagnetic wave therefrom. Thus, the thin-film semiconductor crystalline quality evaluation apparatus (1) and method configured in this manner make it possible to evaluate the crystalline quality even in the above situation where the electrically conductive film (2b) is formed under the semiconductor thin-film (2a).