Stand-off control apparatus for plasma processing machines

A stand-off control apparatus for plasma processing machines which is capable of maintaining optimum stand-off even when a processing speed (F) varies. In a stand-off control apparatus for plasma processing machines which is provided with a microcomputer (4) for maintaining an optimum stand-off (h0) by moving a torch (1) toward a work so that an independently inputted arc voltage V agrees with a speed-corrected target arc voltage (V0(F)) obtained by correcting a target arc voltage (V0), which is stored in advance, by an independently inputted processing speed (F), the microcomputer (4) judges at the time of varying a processing speed (F) whether the processing speed (F) is increased, decreased or kept unchanged, and apply the speed-corrected arc voltage (V0(F)) with respect to a relative case after the lapse of respective delay time ( DELTA t) which is independently stored.