A new method of measuring the longitudinal magneto‐optic effect has been introduced. This method does not require a modulator; instead, the analyzer is rotated and the intensity of light is collected as a function of the analyzer angle. The Fourier analysis of the intensity date versus the analyzer angle yields the information about the rotation angle and the ellipticity of the transmitted light. This method is simple in design as well as fast and accurate in data acquisition by virtue of computer‐assisted data collection. It was applied to the real samples of the optical glasses of Schott—SF2, F2, SF6, and SF10. The rotation angle was linearly proportional to the magnetic intensity and the Verdet constants showed a normal dispersion versus photon energy. The results were in a good agreement with other published values. Some possible applications of the present technique to the measurement of a very small birefringence have been discussed.