SLEWING WORK VEHICLE

PROBLEM TO BE SOLVED: To provide a slewing work vehicle capable of conducting boring work, etc., without caring about the back side because a back part of an upper body structure composed of a seat, an engine, a radiator, a hydraulic pump, etc., arranged on a rotary base frame will not collide with an obstacle at the time of turning. SOLUTION: In a slewing work vehicle, a rotary base frame 2 is rotatably installed on a running device through a rotary base shaft bearing, and a work machine A is pivotally supported at a front end part of the rotary base frame through a work machine pivotal support body to be capable of moving up/down and right/left. In this case, on the rotary base frame 2, a seat 9 is arranged on the left side, the work machine A, a hydraulic fluid tank, and a fuel tank are arranged on the right side, a whole body of them is covered with a bonnet 10, and the bonnet 10 is formed in a semicircular form in such a way that an arc part is diagonal in a plan view. At least a rear largest part of an upper body structure B is set to be within a width of the running device.