A rotation device arrangement includes a structure and a suspension part for suspending the rotation device from a boom. The structure includes a first inner body part and first conduits for leading a pressure medium through the first inner body part. A second outer body part is arranged at least partly around the first inner body part completely rotatably. First connections are fitted for leading the pressure medium through the second outer body part. Second conduits are fitted to at least one of an outer surface belonging to the first inner body part and an inner surface belonging to the second outer body part for leading the pressure medium from the first conduit to the first connections. A bearing is arranged to permit the second outer body part to rotate and to carry loads axially and radially. Second connections attach a direct-drive pressure-medium operated turning device to the structure coaxially to transmit torque.