A simple process enables to synthesize tungsten oxide with various nanomorphologies, i.e. nanorods, nanowires, and nanosheets. The tungsten hexachloride (WCI6) was used as a raw material and the tungsten oxide nanoparticles were obtained by solvothermal treatment with solvents, i.e., ethanol, mixed solvent (ethanol+water), and water, at 200 degrees C for 10 h. The various crystalline phases of tungsten oxide, such as monoctinic W18O49 nanorods, hexagonal WO3 platelets, and monoclinic WO3 nanosheets, were synthesized by simply changing the composition of the solvent. The oxygen, which was contained in water, played an important role in the final tungsten oxide phase. Especially, W18O49 nanorods grew to nanowires as the concentration of WCI6 was decreased. Using this simple process, it will be possible to control the crystalline phase and morphologies of nanostructured tungsten oxide system.