Gallium oxide nanowires were synthesized by electric are discharge of GaN powders mixed with a small amount of Ni and Co. The crystal structure of nanowires was determined by multi-channel X-ray diffractometry (MC-XRD), FT-Raman spectroscopy and transmission electron microscopy (TEM). The analyzed results clearly show that the synthesized nanowires are monoclinic gallium oxide (beta -Ga2O3). Final morphology and microstructure of beta -Ga2O3 nanowires were changed depending on the presence of the transition metals into the nanowires. The beta -Ga2O3 nanowires grown by the assistance of transition metals demonstrate a smooth edge surface while containing twin defects at the center. The transition metals have enhanced the step growth of nanowires. However, in the case of the beta -Ga2O3 nanowires, where the transition metals are not shown on the surface, the nanowires demonstrate rather thin and long shapes with amorphous gallium oxide layers on the nanowire surface.