The invention provides a spectroscopic instrument, which comprises a projecting optical system for projecting a projecting light emitted from a light source, a photodetecting optical system for receiving a reflection light from an object to be measured and for guiding to a photodetection member, and a spectroscope for detecting a condition of the object to be measured based on the reflection light as received by the photodetection member, wherein the projecting optical system and the photodetecting optical system have a projecting system chromatic aberration decreasing component and a photodetecting system chromatic aberration decreasing component which eliminate chromatic aberrations, respectively.