PROBLEM TO BE SOLVED: To provide a combine harvester which is enabled to protect outside of an input pulley 166 and a discharge conveyor drive belt 57 by a tension arm 169.SOLUTION: A combine harvester comprises: a running frame 1 having an engine 7 mounted thereon; a grain tank 6 having a bottom conveyor 60 mounted therein; an input side case 161 disposed on a front face side of the grain tank 6 confronting an engine 7; and a discharge conveyor 8 disposed on an opposite back face side of the grain tank 6, wherein a discharge conveyor driving belt 57 is tensed through a tension pulley 56 between the engine 7 and an input pulley 166 of the input side case 161, wherein a tension arm 169 for supporting the tension pulley 56 is extended to an outer side of the input pulley 166, and wherein the input pulley 166 and the discharge conveyor driving belt 57 are arranged between the input side case 161 and the tension arm 169.