Abstract: This application discloses a spectrophotometer employing a magneto-optic effect which enables quantitative analysis of a sample to be measured by a double beam method. In performing the double beam method for analyzing the sample, a magnetic field is applied to the sample along with linearly polarized light from a light source, the forward scattered light scattered by the sample atoms and the incident linearly polarized light from the sample are converted into two cross-polarized beams of light using an analyzer, and these two beams of cross-polarized light are spectrally analyzed by a single dispersive element. The spectrophotometer of the invention provides an arrangement such that the plane defined by the above-mentioned two beams of light is perpendicular to the plane of dispersion of the dispersive element, and the two beams of light so dispersed are independently detected by separate detectors.