PURPOSE: To unify welding current and after-flow time, by providing a delay circuit which optimizes the after-flow time by setting the command value of the welding current at an adequate value.

CONSTITUTION: A regulator 6 for welding current controls the output current of a control part 16 for output current to a set value and inputs the command value thereof to a delay circuit 17. A solenoid valve 10 is held energized during welding to maintain the flow of a shielding gas, and normally closed contacts 22 are held open. When the contacts 22 are closed by the command for stopping the welding, clock pulses 25 are inputted to a D/A converter 26, and the output 27 thereof, that is, the input 18 of a comparator 18 increases successively by each one pulse until said input is made equal to the input 19 from the regulator 6 and the output 21 of the comparator 18 is made to zero, then the valve 10 is deenergized and the shielding gas is stopped. It is also possible to change the after-flow time simultaneously by such input, that is, the setting of the regulator 6. The welding current and the after-flow time are unifed by determining the optimum value of the relation between the same and selecting the circuit constant of the circuit 17.