Manganese slimes which were formed in the zinc refinery electrolytic cells contained 59.94 % of MnO₂. The recovery process of MnO₂ from the slimes consisted of five steps, i.e., washing the slimes with water, roasting, dissolution of manganese, removal of impurities, and electrolytic synthesis of MnO₂. By X-ray diffraction method it was proved that the recovered MnO₂ had γ-typed crystalline structure.