Indium-doped tin oxide (ITO) nanowires are synthesized in mass production via thermal evaporation of In2O3, SnO, and graphite mixture powders. The transverse sizes of these nanowires range from 70 to 150 nm, and the lengths are up to several tens of micrometers. The three elements In, Sn, and O uniformly distribute over the whole nanowire, respectively. The atomic concentration of In is about 5%. The gas sensors realized from these ITO nanowires are very sensitive to ethanol gas, and the sensitivity is about 40 against 200 ppm ethanol at the work temperature of 400 °C. Both the response and recovery time are shorter than 2 s. These results suggest that ITO nanowires are good candidates for fabricating gas sensors.