To perform satisfactory crater treatment in two-electrode arc welding to perform welding by using a welding torch provided with a consumable electrode 11 disposed within a shielding gas nozzle 43 for discharging a shielding gas 62, and a non-consumable electrode 12, and generating a consumable electrode arc 31 and a non-consumable electrode arc 32.

When ending a welding operation, the crater treatment is performed by extinguishing the consumable electrode arc 31 while keeping continuing feeding of the consumable electrode 11, and melting the consumable electrode 11 by the non-consumable electrode arc 32. Thereby, the consumable electrode 11 is stably melted, and therefore, the generation of sputter can be suppressed. Also, during the crater treatment, the front end of the consumable electrode 11 is put into a short circuit state from a molten pool 2 to keep a heating current supplied to the consumable electrode 11. Further, when ending the crater treatment, the non-consumable electrode arc 32 is extinguished with a delay after stopping feeding of the consumable electrode 11, and thereby the welding of the consumable electrode 11 is prevented.