The detection of oxygenic gases such as CO2, NOx (NO and NO2), and SOx (SO2 and SO3) has become increasingly important for the control of green house atmospheres, combustion processes, air conditioning and pollution. These gases has been generally measured by spectroscopic instruments based on chemical luminescence and infrared absorption. These apparatuses, however, are not only expensive, but also inapplicable to determination of the oxygenic gases concentration because of its maintenance and time-consuming sampling. In contrast, gas sensors using ceramics surpass them in gas-sensing properties such as gas sensitivity, response time and long-term stability, in addition to maintenance and commercial price. Especially, potentiometric gas sensors using solid-state electrolyte attached with nitrate (NaNO3, NaNO2 and so on) have been attracted a great deal of attention from viewpoint of their practical use. These sensor has a high selectivity, because it detects an objective gas from the electrochemical reaction. From this recognition, we started investigations on the gas sensor of this type.