An amperometric limiting current NO2 sensor was fabricated by combining a Na+ conductor (Na superionic conductor, NASICON) with NaNO2 (or NaNO3) layers. The device using NaNO2 gave a much higher NO2 sensitivity at 200 degrees C compared to that using NaNO3. The current response of the NaNO2-attached device was almost linear with the NO2 concentration in the range of 0 to 80 ppm. In addition, the selectivity of the device to NO2 was fairly high with respect to other gases which are usually coexistent in combustion exhausts. A sensing mechanism of the device is discussed briefly.