A work device has a stationary or movable frame which has a substructure fixed to the frame, a rotating head rotatable about a vertical rotational axis on a bearing block of the substructure by a drive mechanism, and an extension arm mounted on a bearing point of the rotating head in a pivotal manner about a horizontal pivot axis. A hydraulic cylinder piston unit has ends fixed to the cylinder and to the piston rod and hinged to hinge points on the extension-arm side and on the rotating-head side with a horizontal hinge axis. The rotating head has a base section arranged on the bearing block and an adapter piece including the bearing point for the extension arm and the hinge point on the rotating-head side for the cylinder piston unit. The base section and the adapter piece can be removably coupled to each other via a separating point.