A spectral distribution measuring device includes an illumination unit configured to illuminate white light to a surface of an object being measured; a slit array having a plurality of slits formed in alignment at equal intervals; a linear image sensor including a light receiving face having a plurality of rectangular pixels adjacently arranged in alignment and a plurality of spectral light-irradiated areas divided in each predetermined number of neighboring pixels; a plurality of areas being measured which is set on the surface of the object being measured, and reflects the light irradiated by the illumination unit to the plurality of slits; and a diffraction unit configured to diffract and disperse reflection light which is reflected from the areas being measured and has passed through each slit, the diffraction unit being disposed such that a direction where a diffraction image expands is inclined at an angle to a direction where the light receiving face expands.