Dynamic interfacial tension at liquid/liquid interface was measured. Surfactants were supplied to the measured point by a transverse mass-transfer induced by Marangoni instability, and we could make a local interface with surfactants where adjacent bulk phases contained almost no surfactant, The dynamics were dominated by desorption kinetics. A simple model was proposed to explain the results. Attractive interaction between surfactants at the interface was estimated by the model and the experiments.