To prevent deterioration of cutting quality even when scraps drop as in small-hole processing and also minimize deterioration of consumables.

While a nozzle 3 is moved/positioned relatively to a work W, plasma arc is generated between the work W and an electrode 5 in the nozzle 3 supplied with plasma gas, and plasma jet of high temperature is injected to cut the work W. A controller 13 issues plasma arc stopping command during the movement before the cutting is completed, resulting in ramping down the plasma arc and cutting off the plasma arc current. For example, if scraps drop in the hole processing, the controller 13 cuts off the plasma arc current so that the ramping-down is completed in keeping with the dropping of the scraps.