To provide a gas analyzer extremely simple in its constitution and constituted so as to prevent an exhaust gas after analysis from being discharged into the atmosphere.

The gas analyzer is equipped with a sampling pipe 8 for collecting the exhaust gas in an exhaust gas passage 2, a stagnation chamber (first and second space parts 4 and 6) for stagnating the exhaust gas collected by the sampling pipe 8, the zirconia type oxygen analyzer probe 11 arranged in the stagnation chamber to analyze the concentration of oxygen in the exhaust gas, the reflux flow channel arranged so as to allow the stagnation chamber to communicate with the inside of the exhaust gas passage 2 to reflux the exhaust gas, after analyzed by the zirconia type oxygen analyzer probe 11, into the exhaust gas passage 2 and an ejector for ejecting compressed air into the reflux flow channel in order to introduce the exhaust gas into the stagnation chamber from the exhaust gas passage 2.