A backpack work machine has a cover member (12) that defines a cooling air passage for forced air cooling around an engine (14) and an exhaust muffler (38). The air passage includes: a first air passage (62) extending along an intake-side lateral face of the cylinder block (18) a second air passage 64 extending along a lateral face of the cylinder block (18), which is at a near side to a recoil starter (32) a third air passage (66) extending along an exhaust-side lateral face of the cylinder block (18) and an outlet passage (70) partitioned from the third air passage (66) by a plate (52). Air flowing through the second air passage (64) and air flowing through the third air passage (66) join at a juncture (72) that bulges outward. The bottom at the portion corresponding to the juncture (72) inclines downward toward the outlet (50a) of the outlet tube (50) of the outlet passage (70) when observed in an elevational view. Thus, the worker using the backpack work machine can be protected against heat generated by the internal combustion engine used to power the work machine.
