The NO2 gas sensor based on SnO2 semiconducting nanowires workable at room temperature has been investigated. The network structure of SnO2 nanowires was fabricated on the electrodes by a simple thermal evaporation process from Sn metal powders and oxygen gas. The diameter of the nanowires was 20-60 nm depending on the processing conditions. When the concentration of NO2 was 10 ppm, the sensitivity of 43, the response time of 38 s, and the recovery time of 25 s were observed at the operating temperature of 200 degrees C. In particular, the operating temperature of the sensor could be decreased down below 50 degrees C by controlling the properties of the nanowires and the structures of the electrodes. The sensitivities were 10-15 when the NO2 concentrations were 10-50 ppm at the operating temperature of 50 degrees C.