Steam reforming of CH4 on microcrystalline metal catalysts dispersed on Sm-doped ceria (SDC) was investigated with the intention of the application to an anode for internal reforming-type solid oxide fuel cells to be operated at medium temperature. Ru- or Ir-dispersed SDC exhibited high catalytic activities and low activation energies; these are potential candidates for that application. The high dispersion of microcrystalline noble metal catalysts results in such a high catalytic activity even with a significantly small amount of noble metal.