PURPOSE: To obtain remote and automatic cutting, simplification of a titled device and prevention of expansion in contamination by allowing the torch nozzle at the tip of a rod in cylinder in a watertight cylindrical body rotating in a circumferential direction in a guiding part enclosing an object to be cut to follow up automatically at a correct distance in said cylinder.

CONSTITUTION: In the case of cutting a large waste object 2 in, for example, a nuclear powder field, in a pool 1, plasma arc cutting is started with a torch nozzle 9. A cylindrical body 5 is rotated by a driving part 15, but there is no entry of water into a guiding part 4. Since the nozzle 9 is operated by a cable 11, the nozzle is reset to the origine after 1/2 turn and is again rotated 1/2 turn in a forward direction. After the end of the required cutting, the object 2 is rotated and is cut in the same manner as mentioned above. If there is a change in the outside diameter of the object 2, said change is detected with a detector 10, and a cylinder 7 is operated, whereby the distance between the nozzle 9 and the object 2 is controlled adequately and automatically.