Gallium-oxide (Ga2O3) nanoparticles and nanowires were synthesized using a direct current arc thermal plasma. Gallium nitrate hydrate (Ga(NO3)3·xH2O) was used as a raw material for the synthesis of the Ga2O3 nanomaterials. (Ga(NO3)3·xH2O) was injected into the area of the thermal plasma in a liquid state with two different solvents, distilled water (H2O) and methyl alcohol (CH3OH). The as-synthesized Ga2O3 nanomaterials were characterized according to their crystallinity and morphology. In the cases of both the H2O and CH3OH solvents, the crystalline monoclinic β-Ga2O3 nanomaterials were synthesized in a reaction tube. Amorphous Ga2O3 nanoparticles were collected in a chamber in the case of the H2O solvent whereas amorphous Ga2O3 nanowires were found in the case of the CH3OH solvent. As a result, β-Ga2O3 nanoparticles, amorphous nanoparticles and nanowires were selectively synthesized by using a thermal plasma process, depending on the collection position of the product and the type of mixing solution.