Ultrafine metal particle-supported carbon particles were synthesized by pyrolysis of polymer particle-metal ions such as Co(II), Ni(II), Cu(II), Ag, Pd(II), and Rh(III) complexes. The sizes of metal particles increased with increasing pyrolysis temperature. Pd and Rh particles were on the whole smaller than were Co, Ni, and Cu, even though the amounts of Pd and Rh ions immobilized were higher. Rh particles supported on carbon particles exhibited high catalytic activity for the decomposition of hydrogen peroxide.