A spectroscopic device that can suppress the occurrence of cross-talk when light beams of different wavelength ranges are optically received is provided. Detected light is made incident to a dichroic minor (hereinafter referred to as "mirror") DM.sub.1 along the perpendicular direction of a photoelectric surface 7. Accordingly, light transmitted through the mirror DM.sub.1 is made incident substantially perpendicular to the photoelectric surface 7. On the other hand, light reflected from the mirror DM.sub.1 is reflected from a main mirror surface 23. At this time, the dichroic mirror array 21 is inclined so that the mirror DM.sub.8 side having the minimum shortest wavelength is nearer to the photoelectric surface 7 than the minor DM.sub.1 side having the maximum shortest wavelength and substantially parallel to the main minor surface 23a, so that light reflected from the main mirror surface 23a is made incident to the mirror DM.sub.2 along the perpendicular direction of the photoelectric surface 7. Accordingly, light transmitted through the mirror DM.sub.2 is made incident substantially perpendicular tote photoelectric surface 7. As described above, the light transmitted through each mirror DM.sub.n is substantially vertical made incident to the photoelectric surface 7, and thus the occurrence of cross-talk can be suppressed.