To provide a flue gas treatment device not using noble metal and ceramic of high heat resistance in an oxidation catalyst.

This flue gas treatment device 30 wherein an exhaust gas including at least one of carbon fine particles and carbon monoxide flows in from an inflow port 31, and the exhaust gas is oxidized and discharged from a discharge port 32, comprises a horn-shaped ventilation part forming body 33 having the wide inflow port 31 and the narrow discharge port 32, and an oxidation treatment part 34 mounted at a peripheral edge part of the ventilation part forming body 33 for oxidizing the exhaust gas.