A walk-behind work machine in which vibration produced by the driving of an engine is not readily transmitted to an operating handle. The work machine includes a work-machine body having a plurality of mounting parts to which an engine is joined. The mounting parts include a high-rigidity mounting part positioned at a maximally rigid part on the work-machine body, and other mounting parts exclusive of the high-rigidity mounting part. The engine is joined securely to the other mounting parts and is joined more loosely to the high-rigidity mounting part than to the other mounting parts.