To obtain a working machine with which the working range can be extended or deep ground improvement can be performed by reducing the size of the working machine to increase the travel of a working body.

A support arm 17 is provided to a body part 5 in a forward protruded relation, and a rotating cylinder 22 for raising/collapsing/rotating the guide body 20 provided to the front end part of the support arm 17 is also provided to the body part. A relay mobile body 24 and the working body 10 are arranged in parallel with each other and are respectively set to the guide body 20 in a forward and rearward slidable manner, and front guide wheels 27 and rear guide wheels 28 are rotatably provided to the front and rear portions of the relay mobile body 24. In the guide body 20 and the working body 10, an acting cylinder 32, provided at a position between the front guide wheels 27 and the rear guide wheels 28, which moves the relay mobile body 24 in the longitudinal direction relative to the guide body 20, by connecting both ends of an advance tensioner 30 and both ends of a reverse tensioner 31, winding the intermediate portion of the advance tensioner 30 around the front guide wheels 27, and winding the intermediate portion of the reverse tensioner 31 around the rear guide wheels 28.