To solve problems in which a pre-flow time of as long as 10-20 seconds is required and it is difficult to determine when welding is started after completion of the pre-flow, in performing welding with special members such as titanium.

In an arc start control method of consumable electrode arc welding, injection of shielding gas starts upon input of a weld start signal in a welding power unit, after a lapse of prescribed pre-flow time, forward feeding of a weld wire to a workpiece starts and also output of the welding power unit starts, and, when an arc is generated with the welding wire in contact with the workpiece by the forward feeding, the feed speed of the welding wire is shifted to a regular feed speed. The method is characterized in that the weld wire is backward fed after the lapse of the pre-flow time and that, when the backward feeding is completed, the weld wire is forward fed to the workpiece.