A combine harvester capable of preventing fine dust from being sucked from a cooling air suction part, comprising a threshing part threshing harvested cereal culms, a sorting part sorting grains threshed by the threshing part, and a prime mover part driving the threshing part and the sorting part. Exhaust gas from an engine installed in the prime mover part is exhausted through an exhaust gas flow passage forming body, and a muffler is installed in the middle of the exhaust gas flow passage forming body. The cooling air suction part is formed in the exhaust gas flow passage forming body positioned on the downstream side of the muffler, a pre-fan is installed in the sorting part, and the cooling air suction part is disposed near the pre-fan. Accordingly, since cooling air into which fine dust is sucked by the pre-fan is sucked from the cooling air suction part to cool the exhaust gas and the fine dust is prevented from being sucked from the cooling air suction part.