To reduce the smell concentration of the bean-roasting exhaust and the concentration of NOx.

In a bean roaster equipped with the roasting chamber 1 that receives a certain amount of raw beans and roasts them with hot air and with the cooling tank 11 that receives the beans roasted in the roasting chamber 1 every when the roasting completes in the chamber 1, the exhaust gas cleaner is equipped with the temperature adjuster 22 utilizing both of the exhaust gas used in the roasting chamber 11 and the exhaust gas used for cooling in the cooling chamber 11 flow in for cooling or heating, and equipped with the catalytic reactor 31 for catalytically decomposing organic nitrogen and deodorizing the exhaust gas passing through the temperature adjuster 22 and the organic nitrogen-decomposing catalyst 33 is set on the upper stream of the exhaust pass of the catalytic reactor 31 and an oxidation catalyst 34 is arranged to the downstream side. The exhaust gas is adjusted temperature for both the nitrogen removal and deodorization at the temperature adjuster, at first the organic nitrogen is removed with the catalyst 33, is deodorized with the oxidation catalyst 34 and is discharged into the atmosphere.