SnO2 is a widely used sensor material that exhibits high sensitivity. It is known for its complex sensing characteristics, and its microstructure is an important parameter related to electrical properties and mechanical rigidity. Understanding of its microstructural effects is therefore essential to examine sensing mechanisms that may apply to industrial devices. In this work, the effect of a sintering process on the electrical properties is investigated. The sintering temperature and the relative density were chosen as process variables. The grain size of the specimen increased as the sintering temperature increased, whereas the relative density did not change. The apparent activation energy for conduction varied as the compacting pressure and the sintering conditions changed. Samples with a high density and large particle size showed low activation energy for conduction and low sensitivity at 375 degrees C. In an attempt to improve the properties, the powder was heat-treated at 1000 degrees C for 10 hours before compacting and sintering. The samples with heat-treated powder showed a slight decrease in the activation energy depending on the density and comparable sensitivity compared to non-treated powder at a high density. Pre-treatment of powder can be a simple means of thermal stability under high operating temperatures.