A method is presented for measuring the angle of optical rotation in the course of a single pulse of radiation with time resolution better than 0.5 nsec. The method is based on the combination of two data channels on a single photodetector, separated in time by an optical delay line. The feasibility of the method is illustrated by studying the dynamics of the rotation of the plane of polarization of radiation from a pulsed dye laser with an optically active object placed in the resonator.