Silk fibroin membrane is the amphoteric ion exchange membrane with the weak acid and base which are composed of amino and carboxyl groups, respectively. In this study ion transport phenomena were investigated using Teorell-Meyers-Sievers (TMS) theory. Membrane potential was measured for KCl, K2SO4, K2HPO4, MgCl2, CaCl2, and MgSO4 aqueous solution. The effective charge density (QCx) and ion mobility ratio of anion to cation (ω-/ω+) in the membrane were calculated by applying TMS theory to experimental results. QCx, was 0.015mol/L, which was one-nineteenth times smaller than that calculated from the data of amino acid content in silk fibroin. ω-/ω+of KCl, CaCl2 and MgCl2 in the membrane were larger than that in water, and ω-/ω+of K2SO4, K2HPO4, and MgSO4were smaller than that in water.