When a membrane system composed of two aqueous phases (W1 and W2) separated by a liquid membrane (M) was adopted, and potential difference, EM(A - B), was applied between two sites (sites A and B) in M, the ion transport reaction from M at site A to M at site B through W1 or W2 (M-W1-M or M-W2-M transport) was found to occur based on the voltammogram recorded by scanning Em(A-B) and measuring the current between sites A and B. The efficiency of M-W1-M or M-W2-M transport was higher when the ratio of the concentration of electrolyte in M to that in W 1 or W2 was lower. An ion transfer reaction at the W 1 \ M or W2 \ M interface in a region between sites A and B (site Q could be realized under the application of Em (A - B). The ion transport from W1 to W2 through a special region of M was also found to be possible under the applied Em(A-B)- Similar ion transport from W1 to W2 occurred even when the Em(A-B) was applied by using chemical reactions instead of an external circuit.