GAS SENSOR

PROBLEM TO BE SOLVED: To provide a gas sensor having high gas selectivity.SOLUTION: A gas sensor (1) comprises electrode pairs (13, 25) formed from detection electrodes (15, 27) and reference electrodes (17, 29) made of different electrode materials on the surface of solid electrolytes (11, 23), which are oxygen ion conductive. The gas sensor (1) detects the concentration of a specific gas on the basis of a potential difference between the electrode pairs (13, 25) by the specific gas in a measurement atmosphere. In particular, as the electrode pairs (13, 25), the gas sensor has a first electrode pair (13) and a second electrode pair (25). The detection electrode (15) of the first electrode pair (25) has a lower layer (19) containing Pt and an upper layer (21) laid above the lower layer (19) and containing MgAlO. The detection electrode (27) of the second electrode pair (25) contains Au. On the basis of the ratio of output from the first electrode pair (13) to output from the second electrode pair (25), the concentration of the specific gas is detected.