PURPOSE: To provide a direct current arc welding machine of long life electrode non-contact arc starting system or a plasma cutter which is noiseless and excellent in characteristic of cable extension.

CONSTITUTION: The output of a 1st direct current power source 1 is supplied to a load through a switching element 11, a 2nd direct power source 10 impressed with direct current high voltage is also connected to the load, at the time of arc actuation, the direct current high voltage is impressed to the load from the 2nd direct current power source 10, a single directional rectifying device 11 is made conductive with the output of a discharge detector 12 to detect the discharge with the 2nd direct current power source 10.