Methanation reactivity was studied for the surface carbon deposited from CO2 on the surface of Rh-bearing activated magnetite. The most active material (Rh=0.83 wt%) for methanation was prepared by the impregnation method at 60-degrees-C and showed 98% conversion at 300-degrees-C. The surface carbon was composed of elemental carbon (alpha-carbon) and polymerized carbon (beta-carbon), the proportion being dependent on the density of carbon deposited. In temperature-programmed surface reaction, the extent of conversion of the alpha- and beta-carbon to CH4 was 0.34 (alpha-carbon) and 0.53 (beta-carbon), respectively., and the total conversion was 0.87. This result indicates that not only elemental carbon but polymerized carbon (beta-carbon) could be converted to CH4 on the Rh-bearing activated (alpha-carbon)magnetite, whereas carbon is not hydrogenated on activated magnetite.