PROBLEM TO BE SOLVED: To improve a structure of a side part cover attached to an engine exhaust side of an engine case to improve rigidity to shaking and distortion of the engine case, and improve detaching/attaching working efficiency of a work component.SOLUTION: There is provided a portable work machine in which an engine is arranged in an internal space of an engine case that is formed in a U-shape in a side view, and which has: a side part cover 6 attached to an engine exhaust side of the engine case and an operation handle 7 arranged on an upper wall of the engine case. The side part cover 6 is divided into a muffler cover 10 covering the engine exhaust portion and a drive part cover 11 covering a rotary drive part driven by the engine, the muffler cover 10 is fixed by a U-shaped root part of the engine case and middle parts of upper and lower plate parts extending from the root part, and the drive part cover 11 is detachably installed between the upper and lower plate parts of the engine case at a front side of the muffler cover 10.
