A new method using non-electrolytic deposition/stripping voltammetry was developed for determining trace amounts of chloride ion in the order of 0.1mg L^-1 in copper electrolyte solutions. It was found, using a silver electrode as the working electrode, that when the electrode was immersed for a certain time in an agitated copper electrolyte solution containing a certain amount of Fe(III) ion, a quantitative amount of chloride ion could be spontaneously collected without applying electric potential. Then the deposited silver chloride on the silver electrode was stripped. One cycle of measurement of this method took approximately 10min, and the relative standard deviation of the measurements of 0.5mg L^-1 chloride ion in a synthetic copper electrolyte solution was 2.0%(n=10). The effect of coexistent substances was examined. The measured concentration of chloride ion was influenced by changes of concentrations of copper (II) ion, sulfuric acid and iron(III) ion. Then, a calibration method using the standard addition method was examined. The time required for the whole procedure of the standard addition method was approximately 60min, and the relative standard deviation of the measurement of chloride ion in diluted copper electrolyte solution was 5.6% (n=6).