We investigated four catalysts for the dry reforming of methane: three Ni-containing natural iron ores (LN, SN, and NN ores) and one Ni-supported ore (Ni-supported NN ore) to solve the problems about unused high-temperature waste heat and CO2 emission in the steel industry. The CO2 conversion ratio was highest for the LN ore (1.18 wt '% Ni), followed by Ni-supported NN (1.0 wt % Ni), SN (0.30 wt % Ni), and NN (0 wt % Ni) ores. The CO2 conversion ratio of the LN ore was much higher than that of the Ni-supported NN ore, despite the fact that they contained almost the same amount of Ni. This is because the LN ore had a higher surface area and a higher nickel dispersion. Transmission electron microscopy with energy dispersive X-ray spectroscopy revealed that Ni existed quite finely in the LN ore but existed as a larger particle (20 nm) in the Nisupported NN ore. Smaller Ni particles have a higher surface area, resulting in the higher catalytic performance of the LN ore. More CO2 and CH4 reacted and higher amounts of H-2 and CO were produced with the LN ore catalyst compared to the uncatalyzed reaction. The LN ore showed more reduction at higher temperatures, and metallic iron and nickel were produced above 1073 K; reduction did not progress past Fe3O4 at lower temperatures.