To sample a gas to be analyzed of an accurate amount by mixing the gas to be analyzed of an equal amount to a sampled amount of a diluting gas with the diluting gas.

A control circuit 7 operates an air sampling pump 10 to sample an air of an amount proportional to an exhaust gas flow rate to be detected by an exhaust gas flow rate sensor 16 from an air introducing tube 3 and controls an air sampling controller 9. Thus, since a part of the air introduced from the tube 3 is sampled at an upstream side of a dilute tube 2, the exhaust gas of an amount corresponding to the sampled air amount is introduced into the tube 2 via a gas introducing tube 5. This exhaust gas is mixed with the air in the tube 2. A mixed gas of the exhaust gas and the air is supplied to an exhaust gas analyzer via a mixed gas exhaust tube 4. And, it is controlled so that the mixed gas exhaust amount becomes equal to the air introducing amount. Thus, only a detecting error of the air sampled amount of the controller 9 affects an influence to the exhaust gas introducing amount, and its value is very small. Accordingly, the exhaust gas of more accurate amount can be introduced into the dilute tube.