To improve an arc starting characteristics of a DC arc welding machine and arc regeneration in generating excessive short circuiting between a welding torch and a base metal.

Outputs of voltage supply power generation coils A1, A2 and electric current supply power generation coils A3-A8 arranged to a magnet generator driven by an internal combustion engine are supplied to between output terminals of a welding machine t1, t2 respectively through diode bridge full wave rectifiers and mixed bridge full wave rectifiers Re21-Re26. An electric current increase command circuit B, which generates an electric current increase command signal when the voltage between the output terminals t1, t2 is lowered to a set value or lower, and a trigger control device ST, which gives a trigger signal to a thyrister of the mixed bridge full wave rectifiers Re21-Re26 so as to increase a welding current larger than a set value when an electric current increase command signal generates, are arranged.