Disclosed are a spectroscopic optical system and a spectrometer both enabling vertical illumination by means of an optical system using only refractive lenses and enabling wide-band color correction in the DUV-UV (190 to 400 nm) range. The spectroscopic optical system and spectrometer each comprise a light source (100), a folding mirror (110), a field stop (120), an object-side focusing lens system (130) for focusing light onto a sample, an image-side focusing lens (140) disposed on the image forming plane of the object-side focusing lens system, and a spectroscope (150) for dispersing regularly reflected light from the sample. The object-side focusing lens system (130) and the image-side focusing lens system (140) are each a spectroscopic optical system corrected with respect to color in a broad band of wavelength from 190 to 400 nm and configured from only refractive lenses enabling vertical illumination. The working distance (WD) of each lens is set shorter than a predetermined distance, and the doublet interval (D) is set longer than a predetermined distance.