PURPOSE: To improve the ease of handling of an object to be cut and to make the expansion in targets possible in a plasma cutter by using split guiding parts.

CONSTITUTION: An upper guiding part 4 is beforehand removed from a driving shaft 3 for hoisting. An object to be cut is set on a stand 2 by means of a crane or the like, and the shaft 3 is rotated to move a lower guiding part 5 upward or downward, thereby aligning the center of the object to be cut to the top end of the guide 5. The part 4 is moved downward and is placed on the part 5. A cylinder is operated to advance a torch nozzle 17 to maintain the spacing from the object adequately. When the positioning of the nozzle 7 ends, a plasma arc is generated and cutting is started; at the same time the torch 17 is turned in the circumferential direction of the object, whereby the object is cut.