A welding apparatus comprising: a welding power source configured to output current between a consumable electrode and a workpiece; and an AC pulse control unit configured to control the welding power source to repeat a sequence including: outputting a positive peak current from the workpiece to the consumable electrode during a positive peak period; outputting a positive base current from the workpiece to the consumable electrode and subsequently outputting a negative base current from the consumable electrode to the workpiece during a first base period, an absolute value of the positive base current and the negative base current being less than the positive peak current; outputting a negative peak current from the consumable electrode to the workpiece during a negative peak period following the first base period, an absolute value of the negative peak current being greater than the absolute value of the positive base current and the negative base current; and outputting the negative base current and subsequently outputting the positive base current during a second base period following the negative peak period, characterized in that the welding apparatus further comprises a switching timing setting unit which is configured to output the positive base current for a longer period of time than the negative base current during the first base period, and to output the negative base current for a longer period of time than the positive base current during the second base period. a welding power source configured to output current between a consumable electrode and a workpiece; and an AC pulse control unit configured to control the welding power source to repeat a sequence including: outputting a positive peak current from the workpiece to the consumable electrode during a positive peak period; outputting a positive base current from the workpiece to the consumable electrode and subsequently outputting a negative base current from the consumable electrode to the workpiece during a first base period, an absolute value of the positive base current and the negative base current being less than the positive peak current; outputting a negative peak current from the consumable electrode to the workpiece during a negative peak period following the first base period, an absolute value of the negative peak current being greater than the absolute value of the positive base current and the negative base current; and outputting the negative base current and subsequently outputting the positive base current during a second base period following the negative peak period, characterized in that the welding apparatus further comprises a switching timing setting unit which is configured to output the positive base current for a longer period of time than the negative base current during the first base period, and to output the negative base current for a longer period of time than the positive base current during the second base period. outputting a positive peak current from the workpiece to the consumable electrode during a positive peak period; outputting a positive base current from the workpiece to the consumable electrode and subsequently outputting a negative base current from the consumable electrode to the workpiece during a first base period, an absolute value of the positive base current and the negative base current being less than the positive peak current; outputting a negative peak current from the consumable electrode to the workpiece during a negative peak period following the first base period, an absolute value of the negative peak current being greater than the absolute value of the positive base current and the negative base current; and outputting the negative base current and subsequently outputting the positive base current during a second base period following the negative peak period, characterized in that the welding apparatus further comprises a switching timing setting unit which is configured to output the positive base current for a longer period of time than the negative base current during the first base period, and to output the negative base current for a longer period of time than the positive base current during the second base period.