A spectroscopic unit comprising: a linear variable filter for spectrally dispersing target light to be measured, on a wavelength-by-wavelength basis, the filter having a transmission wavelength which varies depending on an incident position along a first direction as a given one direction; and a light-receiving section for receiving wavelength-separated light components as light components spectrally dispersed by the filter, and outputting signals corresponding to respective intensities of the received wavelength-separated light components, wherein the filter comprises a plurality of optical filter elements (31, 32) sequentially arranged in a direction from an incident side to an output side of the target light, wherein a first optical filter element as one of the plurality of optical filter elements (31, 32) is rotated, by a given angle, about a rotational axis defined along a third direction orthogonal to each of the first direction and a second direction extending from the incident side toward the output side of the target light, or rotated, by a given angle, about a rotational axis defined along the first direction, and thereby disposed inclinedly with respect to a second optical filter element disposed in adjacent relation to the first optical filter element, and wherein the filter comprises two optical filter elements (31, 32) consisting of first and second optical filter elements (31, 32) sequentially arranged in the direction from the incident side to the output side of the target light, and wherein, in order to eliminate multiple-reflection in which the target light travels back and forth between the first and second optical filter elements (31, 32) N times, the given angle is set to satisfy the following conditional formulas and: L 1 tan φ + 2 L 1 ∑ n = 1 N − 1 tan 2 n θ + φ + L 2 tan 2 N θ + φ > x 1 2 + x 2 2 L 2 tan φ + tan 2 θ + φ > x 2, where: L1 denotes a distance, air conversion length, between the first and second optical filter elements (31, 32); L2 denotes a distance, air conversion length, between the filter and the light-receiving section; X1 denotes a width of the filter along the third direction; X2 denotes a width of the light-receiving section along the third direction; φ denotes an orthogonal-directional maximum incident angle of the target light entering the second optical filter element; and θ denotes the given angle. a linear variable filter for spectrally dispersing target light to be measured, on a wavelength-by-wavelength basis, the filter having a transmission wavelength which varies depending on an incident position along a first direction as a given one direction; and a light-receiving section for receiving wavelength-separated light components as light components spectrally dispersed by the filter, and outputting signals corresponding to respective intensities of the received wavelength-separated light components, wherein the filter comprises a plurality of optical filter elements (31, 32) sequentially arranged in a direction from an incident side to an output side of the target light, wherein a first optical filter element as one of the plurality of optical filter elements (31, 32) is rotated, by a given angle, about a rotational axis defined along a third direction orthogonal to each of the first direction and a second direction extending from the incident side toward the output side of the target light, or rotated, by a given angle, about a rotational axis defined along the first direction, and thereby disposed inclinedly with respect to a second optical filter element disposed in adjacent relation to the first optical filter element, and wherein the filter comprises two optical filter elements (31, 32) consisting of first and second optical filter elements (31, 32) sequentially arranged in the direction from the incident side to the output side of the target light, and wherein, in order to eliminate multiple-reflection in which the target light travels back and forth between the first and second optical filter elements (31, 32) N times, the given angle is set to satisfy the following conditional formulas and: L 1 tan φ + 2 L 1 ∑ n = 1 N − 1 tan 2 n θ + φ + L 2 tan 2 N θ + φ > x 1 2 + x 2 2 L 2 tan φ + tan 2 θ + φ > x 2, where: L1 denotes a distance, air conversion length, between the first and second optical filter elements (31, 32); L2 denotes a distance, air conversion length, between the filter and the light-receiving section; X1 denotes a width of the filter along the third direction; X2 denotes a width of the light-receiving section along the third direction; φ denotes an orthogonal-directional maximum incident angle of the target light entering the second optical filter element; and θ denotes the given angle., where: L1 denotes a distance, air conversion length, between the first and second optical filter elements (31, 32); L2 denotes a distance, air conversion length, between the filter and the light-receiving section; X1 denotes a width of the filter along the third direction; X2 denotes a width of the light-receiving section along the third direction; φ denotes an orthogonal-directional maximum incident angle of the target light entering the second optical filter element; and θ denotes the given angle.