A multistage electrodialysis with reflux flow is proposed for the separation of two metal ions. Separation of potassium ion and sodium ion has been investigated by use of bath dialysis with and without electric field and continuous electrodialysis with a four-stage dialyzer. The difference in the permselectivity between the dialysis with and without electric field was not appreciable for the system of potassium and sodium ions with the cation exchange membrane used. For continuous electrodialysis, the concentration ratio between potassium and sodium ions in the top product (the outlet solution from the recovery side) increased with the reflux flow rate and the number of stages. When the reflux flow rate was zero, the concentration ratio with the four-stage dialyzer was 1.5 which was almost the same as with the two-stage dialyzer consisting of a single membrane, while the ratio reached 3.6 for a reflux ratio of 0.7.