A solid electrolyte type sulfur dioxide (SO<sub>2</sub>) gas sensor that can operate at moderate temperatures was fabricated using Zr<sup>4+</sup> ion conducting Zr<sub>39/40</sub>TaP<sub>2.9</sub>W<sub>0.1</sub>O<sub>12</sub> solid electrolyte with 0.7La<sub>2</sub>O<sub>2</sub>SO<sub>4</sub> − 0.3(0.8Li<sub>2</sub>SO<sub>4</sub> + 0.2K<sub>2</sub>SO<sub>4</sub>) having a large surface area and Zr metal as the auxiliary sensing electrode and reference electrode, respectively. Since the present sensor showed a quantitative, reproducible and rapid response which obeys the theoretical Nernst relationship even at 400 °C, it is a potential on site SO<sub>2</sub> gas sensing tool operable at moderate temperatures around 400 °C.