To provide a Fabry-Perot spectrometer for detecting spatially differed spectral characteristics of a dispersing light source.

A Fabry-Perot spectrometer 1 is formed of a Fabry-Perot etalon 15, a pair of cylindrical lenses 11, 14 arranged so that the top parts are mutually parallel to diffuse the light from a light source vertically to each top part, a focusing lens assembly 16, and a detector 17 arranged on the focal surface of the focusing lens assembly 16. A detecting lens assembly is formed of two cylindrical lens, which are provided so that the top part of one cylindrical lens is parallel to the top part of the cylindrical lens for diffusing the light, and the top part of the other cylindrical lens is vertical to the top part of the cylindrical lens for diffusing the light, so that the false signal of spectrum is prevented.