The Boudouard reaction, that is, reaction of activated carbon with carbon dioxide to carbon monoxide, is carried out at 773 Ei in a stirred mill reactor. The mean diameter of activated carbon changes from 44 to 1.2 mum by the grinding. The reaction occurs by grinding activated carbon in the reactor and the reaction rate increases with the increase of stirring rate of ball. The reaction rate also increases by addition of iron powders as the catalyst and the catalytic activity of iron powders is changed by the kinds of ball (iron or zirconia) and the diameter of iron powders. This catalytic activity is preserved after the stirring of ball is stopped. However, the reaction rate decreases with time and the decrease rate is dependent on the kinds of bail and the diameter of iron powders. Nickel oxide powders show catalytic activity by mixing with iron ball but not with zirconia ball. To investigate the interaction between activated carbon and iron, the surfaces are observed by using a scanning electron microscope (SEM) and energy dispersive X-ray analyzer (EDX).