The invention provides an inclined incidence broadband spectrometer which has the advantages of easiness for adjusting and focusing, no colour difference, polarization property retaining and simple structure. The inclined incidence broadband spectrometer comprises at least one polarizer, at least one curved reflection component and at least two planar reflection components. The inclined incidencebroadband spectrometer changes the propagation direction of a beam by utilizing the planar reflection components and can compensate for polarization change resulted from a reflection spotlighting unit so that the polarization property of the beam after passing through the polarizer can be kept same in the event of being incident in an inclined manner and converged on the surface of a sample. The inclined incidence broadband spectrometer disclosed by the invention can be used for measuring an optical constant and thin film thickness of a sample material with high precision and/or analyzing a critical dimension (CD) or three-dimensional shape of a sample with a periodic structure.