PURPOSE: To enable preheating and cutting-off at a low cost by preheating a metallic material to the firing temp. with electromagnetic heating, jetting gaseous oxygen into the preheating range from a jetting nozzle and cutting off the metallic material with burning.

CONSTITUTION: Plural sector-shaped coil pairs 23 for induction heating constituted with the coils 23R and 23L are arranged while centering the jetting nozzle 21 jetting the gaseous oxygen to the metallic material W. In the coil pair 23R and 23L, the coils are wound on iron cores in mutually the reverse direction and indivudually connected with high frequency electric sources. The coil pair 23 are arranged on a supporting member 27 of an electric insulating body and the jetting nozzle is inserted into a nozzle inserting hole 37 at the center part. For example, in the case the metallic material W is SPC, the preheating to 1200°C firing temp. till about 0.5mm depth from the surfaces of one pair of coils can be executed, and the preheating range exists in the whole direction while centering the jetting nozzle 21. The gaseous oxygen is jetted from the jetting nozzle 21 and shifted to enable the cutting-off of the metallic material W.