Superconductivity and magnetic transition in SmFePO were examined by electric, magnetic, Fe-57 Mossbauer, and Sm-149 nuclear resonant forward-scattering (NRFS) measurements. Zero resistivity and negative magnetic susceptibility were observed in an undoped SmFePO, indicating superconducting transition temperature (T-c) of similar to 3 K. T-c in undoped SmFePO appears in a narrow region of lattice constants with an optimum conductivity. Furthermore, in relation to magnetic susceptibility, NRFS spectra verify that magnetic moments of Sm3+ ions order antiferromagnetically below magnetic transition similar to 5 K, accompanying a discontinuous drop in electrical resistivity, whereas Fe-57 Mossbauer spectra show that magnetic moments of Fe are quenched. These results indicate the coexistence of superconductivity and magnetic ordering in a crystallographic unit cell of SmFePO.