The structural change of Fe3C and Fe5C2 by mechanical alloying of their elemental powders was studied with X-ray diffraction and Fe-57 Mossbauer spectroscopy. X-ray diffraction patterns showed the orthorhombic phase Fe3C in the first stage of milling, but the hexagonal phase in the second stage. Amorphous phase was not obtained in both compositions. Fe-57 Mossbauer spectra changed from alpha -Fe, H-int.=330kG, to a ferromagnetic sextet, H-int.=205kG, in the first stage and split into two ferromagnetic ones, H-int.=165 and 210kG in the second stage.