A spectroscope comprising: a beam deflector that includes an electro-optic crystal, having an electro-optic effect, and paired electrodes (192, 193) used to apply an electric field inside the electro-optic crystal, wherein the beam deflector is configured to deflect and disperse incident light in accordance with the wavelength range of the light; and wavelength selection means for selecting light having an arbitrary wavelength from the light dispersed and output by the beam deflector, wherein the wavelength selection means is a slit plate, wherein, at the least, either an input end or an output end of the beam deflector is wedge shaped and configured to disperse the light in accordance with the wavelength range of the light, by gradually reducing the length of the beam deflector in the direction of the optical axis of incident light from the first face, where the first electrode of the paired electrodes is located, toward the second face, opposite the first face, where the second electrode of the paired electrodes is located, wherein the beam deflector disperses the incident light, which has a plurality of wavelengths, to different directions in accordance with the wavelength by applying a voltage to the paired electrodes and outputs the incident light at different deflection angles in accordance with the applied voltage, wherein the voltage is applied in a first voltage applied state in which the voltage is applied to the paired electrodes (192, 193) for the detection of the light having the shortest wavelength in a desired wavelength range for detection, and in a second voltage applied state in which the voltage is applied to the paired electrodes (192, 193) for the detection of the light having the longest wavelength in the desired wavelength range for detection, and wherein the wavelength selection means is arranged at the position that is on the light axis of the shortest wavelength light in the desired wavelength range for detection in the first voltage applied state, and that is on the light axis of the longest wavelength light in the desired wavelength range for detection in the second voltage applied state. a beam deflector that includes an electro-optic crystal, having an electro-optic effect, and paired electrodes (192, 193) used to apply an electric field inside the electro-optic crystal, wherein the beam deflector is configured to deflect and disperse incident light in accordance with the wavelength range of the light; and wavelength selection means for selecting light having an arbitrary wavelength from the light dispersed and output by the beam deflector, wherein the wavelength selection means is a slit plate, wherein, at the least, either an input end or an output end of the beam deflector is wedge shaped and configured to disperse the light in accordance with the wavelength range of the light, by gradually reducing the length of the beam deflector in the direction of the optical axis of incident light from the first face, where the first electrode of the paired electrodes is located, toward the second face, opposite the first face, where the second electrode of the paired electrodes is located, wherein the beam deflector disperses the incident light, which has a plurality of wavelengths, to different directions in accordance with the wavelength by applying a voltage to the paired electrodes and outputs the incident light at different deflection angles in accordance with the applied voltage, wherein the voltage is applied in a first voltage applied state in which the voltage is applied to the paired electrodes (192, 193) for the detection of the light having the shortest wavelength in a desired wavelength range for detection, and in a second voltage applied state in which the voltage is applied to the paired electrodes (192, 193) for the detection of the light having the longest wavelength in the desired wavelength range for detection, and wherein the wavelength selection means is arranged at the position that is on the light axis of the shortest wavelength light in the desired wavelength range for detection in the first voltage applied state, and that is on the light axis of the longest wavelength light in the desired wavelength range for detection in the second voltage applied state.