PURPOSE: To achieve the stabilization of a crater part by setting the 1st welding conditions during welding at the constant welding current conditions in which no pulses are included and the 2nd welding conditions at the end of welding at the welding current conditions in which the combined pulses of a pulse current supply source and a constant speed wire feed speed are included.
CONSTITUTION: The output end of a current supply source 1 is connected in parallel with a pulse current supply source 2 through contacts 12, 13, and current is supplied from the connection point of the contacts 12, 13 to an electrode wire 4 through a power feed tip 6. On ther other hand, the electrode wire 4 is fed to the direction of base metals 5 by the driving roller 8 mounted to the shaft of a motor 7 which is driven by a wire feed circuit 3, thereby connecting the arc 9. Here, during regular welding, the contacts 12, 14 are closed and welding is performed by the combination of the speeds set by the current supply source 1 and a wire speed regulator 10. The contacts 12, 14 are opened and the contacts 13, 15 are closed by the crater signal on the verge of the welding end and small current pulse welding is performed by the combination of the speeds set by the pulse current supply source 2 and a wire speed regulator 11.