Dynamic interfacial tensions and interfacial rheological properties for a oil/water interface were measured by the pendent drop technique in the presence of a surfactant. In the measurement, the pendent drop was expended or contracted at a capillary tip and the rheological properties were calculated by the drop shape analysis[1]. With this technique, static and dynamic interfacial tensions, interfacial modulus (elasticity) can be calculated. Also the relaxation experiment was carried out with the technique. The adsorption kinetics of the surfactant can be studied by the relaxation experiment.