Effects of potassium chloride on the reduction of iron oxides were investigated by using dense hematite, magnetite, and wustite samples prepared by the oxidation of electrolytic iron plates.The addition of small amount of KCl to the surfaces of oxide samples was found to greatly increase the reduction rate of all the reduction steps: Fe2O3 →Fe3O4, Fe3O4→FeO, and FeO→Fe.Reduction of hematite with KCl addition produced very porous magnetite having larger contact area with reducing gas. In the reduction of magnetite with KCl addition, the grain boundary on the surface was strongly eroded and distorted wustite crystals were formed on the magnetite surface. These phenomena were considered to be responsible for the accelerating effects of KCl on the reduction of hematite and magnetite. However, the accelerating effect of KCl on wustite reduction could not be clarified in terms of morphology.