Disclosed is a method for a repeated electroplating of a workpiece to be plated as a cathode by using an insoluble anode in a plating vessel accommodating a copper sulfate plating bath, wherein a copper dissolution vessel different from the plating vessel is provided, the plating bath is transferred to the copper dissolution vessel and is returned from the copper dissolution vessel to the plating vessel for circulating the plating bath between the plating vessel and the copper dissolution vessel, copper ion supplying salt is charged into the copper dissolution vessel and dissolved in the plating bath so that copper ions consumed by the plating can be replenished, and the workpiece to be plated is continuously electroplated, characterized in that the plating bath is permitted to transfer between the anode side and the cathode side, and the plating bath is returned to vicinity of the anode in the return of the plating bath from the copper dissolution vessel to the plating vessel. Plating performance impairing components, which are produced when the copper ion supplying salt is dissolved in the plating bath for replenishing the copper ions, are oxidized and decomposed, whereby defective plating due to the presence of the plating performance impairing components can be prevented.