Astudy for electrodialytic recovery of waste water was made in the nickel electroplating process. Ey the use of the electrodialysis equipment. rinsing waste water is desalted and reused for rinsing, while nickel salt is concentrated and recovered to the plating bath. Although conventional electrodialysis equ.ipmMt is able to apply in this process. proper pretreatment and suitably designed operation condition of the electrodialysis unit are needed for a long term stable o_Deration. Electrodialysis technique , which was developed mainly for sea water concentration and water desalination, has long developing history of over a qnarter century and has been worldwidely commercialized. Recently, there are many commercial scale applications in waste water treatment and one of the tYpical example is the treatment of metaI finishing waste water, Special features of the electrodialysis technique are summar ized as foU.ows. l Electrolyte solution is concentrated to 20% or more, according to the Condition of feed solution. l Electrolyte solution is desalted to 100-200 ppm or less. *Concentration ratio of the concentratestreamanddiluate streamis attained to 100 in an electrodiaIyzer. l Electrolyteis separated from organic nonelectrolyte in aqueous solution. * In neutral, acidic or slightly basic condition ,ion-exchangemembraneis durable for a long Period without any change of electrochemical properties. By these properties, dilute waste water of the electroplating process is advantageously treated by the electrodialysis technique to reuse as the rinsingwaterandto recovervaluable constituents.