Electrolytic manganese dioxide characterized by having a surface sulfate (SO4) content of smaller than 0.10% by weight and a JIS-pH value, as measured according to JIS K1467, of at least 1.5 but smaller than 3.5, preferably at least 2.1 but smaller than 3.2 is provided. Preferably 3% to 25% in number of the fine particles of the manganese dioxide have a particle diameter of not larger than 1 μm. A battery provided with a cathode made from the electrolytic manganese dioxide as active material exhibits good high-rate discharge characteristics and good resistance to metal corrosion.