A spectroscope is equipped with a temperature compensation mechanism that can reliably reduce a drift of a spectral image in the wavelength dispersion direction caused by a change in the environmental temperature irrespective of the form of the spectroscope. The spectroscope is provided with a first support member 17 that integrally supports an incidence member 11, a collective optical system 13 and a detection element 15, a second support member 21, made of a material different from the first support member, that supports a wavelength dispersion element 14, and a transmission member 24, 25 that transmits a contraction/expansion amount of the first support member to the second support member when environmental temperature changes. The second support member includes a deformation member 28 that elastically deforms, when environmental temperature changes, in accordance with a difference between its own contraction/expansion amount and the contraction/expansion amount of the first support member and a rotation member 26 that rotates minutely in accordance with elastic deformation of the deformation member. The said wavelength dispersion element is mounted on the rotation member in such a way that its wavelength dispersion direction is oriented perpendicular to the axial direction of the rotation member.