A simulation for multistage electrodialysis for separation of metal ions is developed, The experimental results for the separation of potassium and sodium ions by a 4-stage electrodialyzer are compared, and can be satisfactorily reproduced by the present simulation method. It is observed that the separation factor increases largely with increasing stage number and flow rate of reflux, The increase in the stage number is effective to achieve a large separation factor and a large recovery fraction of potassium.