Spectrofluorophotometer with monitor detector for light source

A spectrofluorophotometer comprising a light source, an excitation spectroscope for spectralizing the light from said light source, an excitation slit member provided between said light source and said excitation spectroscope and having inlet slits, into which the light from said light source is introduced, and outlet slits, from which the light from said excitation spectroscope is discharged, a beam splitter for splitting the light from said excitation spectroscope, a monitoring detector for detecting one of the beams from said beam splitter, a sample to which the other beam from said beam splitter is applied, a fluorescence spectroscope for spectralizing the fluorescence from said sample, a fluorescence slit member provided between said sample and said fluorescence spectroscope and having inlet slits, into which the fluorescence from said sample is introduced and outlet slits, from which the light from said fluorescence spectroscope is discharged, a detector for detecting fluorescence from said fluorescence spectorscope, a computing element for processing signals from said monitoring detector and said fluorescence detector, and intercepting means provided at least between said light source and said excitation spectroscope for intercepting the light directed from said light source to said monitoring detector and to said fluorescence detector and for enabling at least measurement of deviation of a zero point for said monitoring detector, said monitoring detector supplying a signal indicative of the zero point deviation to said computing element, and said computing element enabling proper measurement by said spectrofluorophotometer in accordance with the zero point deviation of said monitoring detector.