An electrochemical method was proposed as one of the techniques to measure a diffusion coefficient of a solute in liquid metal; the diffusion coefficient was evaluated from the results of chronopotentiometry using a liquid metal electrode containing the solute. Diffusion coefficients of rare-earths (La, Pr, Nd, Gd, Y and Sc) in liquid Cd metal, which were inevitable physical constants to analyze pyrometallurgical reprocessing for spent nuclear fuels kinetically, were measured in LiCl-KCl melts. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3593048] All rights reserved.