To provide a color tone adjusting device by which the color tone of a luminous flux is adjusted with a simple construction, to provide a light source device, and to provide a spectrum measurement device.

The color tone adjusting device (10) includes a dispersion element (11) dispersing an input luminous flux (IL) for each wavelength, a first imaging optical system (12) imaging luminous fluxes dispersed by the dispersion element (11), a transmittance variable part (13) wherein a plurality of transmittance variable elements (132) variably changing transmittance (T) correspondingly to the plurality of luminous fluxes dispersed on an imaging surfaces by the imaging optical system are disposed and a composite optical system (14) combining the plurality of luminous fluxes which have passed through the transmittance variable part (13) and emitting an output luminous flux (OL).

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