A mixed-potential type stabilized zirconia (YSZ)-based gas sensor using columbite type composite oxide sensing electrode was developed and fabricated, aiming at sensitive detection of ethanol. Among the different oxide sensing electrodes (SEs) developed, the sensor attached with ZnNb₂O6-SE was found to achieve the largest sensitivity to ethanol at 625℃. Furthermore, the result of the effect of sintering temperature on sensing characteristic showed that the sensor utilizing ZnNb₂O₆-SE sintered at 1000℃displayed the highest response of -175 mV to 100 ppm ethanol and a low detection limit of 0.5 ppm at 625℃. Delta V of the present sensor exhibited a segmentally linear relationship to the logarithm of ethanol concentration in the ranges of 0.5-5 ppm and 5-200 ppm, for which the sensitivities were -29 and -112 mV decade(-1), respectively. Moreover, the fabricated device also displayed fast response and recovery times, good repeatability, small fluctuation during 30 days continuous high temperature of 625℃measured periods, and acceptable selectivity to some other interfering gases. Additionally, the sensing mechanism involving mixed potential was further demonstrated by polarization curves.