The utility model provides a combine harvester capable of well conducting threshing treatment for a long time. An external mounting cover (21) used for covering the machine body transverse side external portion of a threshing device is arranged on a traveling machine body. The threshing device is provided with a threshing chamber (29) used for threshing crops through a threshing barrel (27) and receiving nets (38A1 and 38A2) in the internal space defined by side plates (8A) and a top plate (26) from left to right. The external mounting cover (21) is arranged to be changed in the state of a side plate (31) covering the external mounting cover side or in the state of opening the side plate (31) on the external mounting cover side towards the external side, the side plate (31) on the external mounting cover side can be detachably arranged, and a guide plate (45) which is more located on the internal side of the threshing chamber when more reaching the lower side in a tilting posture is arranged on the threshing chamber side portion of the side plate (31) on the external mounting cover side.
