A spectroscope of the present invention includes a concave diffraction grating which disperses incident light, an incident light introduction unit which introduces incident light into the concave diffraction grating, and an outgoing light receiving unit which receives outgoing light dispersed for different wavelengths by the concave diffraction grating. The spectroscope further includes an incident aperture which limits an incident angle of light emitted by the incident light introduction unit to the concave diffraction grating, and an outgoing aperture which limits an outgoing angle of outgoing light dispersed for different wavelengths by the concave diffraction grating to the light receiving unit. The spectroscope is constructed so that relatively rotational transfer of at least two out of the concave diffraction grating, the incident aperture and the outgoing apertures can be performed along a Rowland circle which the concave diffraction grating forms.