A study on the formation of iodate produced by oxidation of iodide was performed with cyclic voltam-metry and polarization curve measurement in acidic media on the Ti/RuO₂/MnO₂ electrode prepared by thermal de-composition method. Iodide is oxidized to iodine by the first reversible electrode reaction and then iodine is oxidized to iodate by the se-cond irreversible electrode reaction. Each step of electrode reaction is controlled by diffusion and the reaction rate of the first step is relatively faster than the second step. The effect of pH on formation of iodine is negligible and the reaction rate of the second step is become slow accor-ding to pH increase in acidic media.