To provide a spectral device that has a high detection efficiency in a wide wavelength band, using a VPH.

A spectral device 1 includes, at least: a first VPH diffraction grating (a transmission type VPH diffraction grating 2a); and a second VPH diffraction grating (a transmission type VPH diffraction grating 2b). 0-order diffraction light L0 to be generated by the first VPH diffraction grating (the transmission type diffraction grating 2a) is made incident to the second VPH diffraction grating (the transmission type VPH diffraction grating 2b). An incidence angle to be made incident to the first VPH diffraction grating and an incidence angle of the 0-order diffraction light to be made incident to the second VPH diffraction grating are different from each other.