A carbon dioxide gas sensor was fabricated by using a trivalent Al3+ ion conducting Al-2(WO4)(3) single crystal solid with an oxide ion conducting stabilized zirconia and Li2CO3 as an auxiliary electrode. The sensor response was rapid and reproducible enough for a practical application. In addition, the sensor output was stable and the present sensor would be one of superior promising tool with a compact and maintenance-free type CO2 gas sensing.