The oxidation removal of Cu from carbon saturated iron via Ag phase was tried at 1523K. In addition, the thermodynamic data, which are necessary to know lowering limit of Cu content of carbon saturated iron by this method, are measured. The distribution ratio between carbon saturated iron and silver, L_Cu(mass%)(=[mass%Cu]_{(in Ag)}/[mass%Cu]_{(in Fe–C)}) and the activity coefficient of Cu in carbon saturated iron, γ°_{Cu(in Fe–C)}, are determined to be 7.15 and 50.2 at 1523K, respectively. By using these values, the lowering limit of Cu content of carbon saturated iron is calculated to be 0.21 mass% in oxygen atmosphere (1 atm) at 1523K under the condition that the activity of CuO_x equals to be unity. As the experimental results of Cu oxidation removal from carbon saturated iron via Ag phase, the Cu content of carbon saturated iron is actually reduced to 0.3–0.6 from 4 mass%, and it is found that the copper in molten iron can be removed by the method proposed in the present study.