To improve detection precision of constriction of a droplet in consumable electrode arc welding.

In the method of detecting/controlling the constriction in consumable electrode arc welding, by which the constriction of the droplet is detected by the fact that the change of resistance value between a consumable electrode 1 and a base metal 2 reach a constriction detection reference value Vtn, and when a constriction phenomenon is detected, output control is performed so that an arc is regenerated in the state of a low current value by reducing a welding current Iw, a constriction detecting time from the point of time when constriction phenomenon is detected to the point of time when the arc is regenerated is detected for each short circuit, when the constriction detecting time is not longer than the lowest limit time, one is subtracted from the counter value, when the constriction detecting time is not longer than the upper limit time, one is added to the counter value and, when the counter value reaches the minus reference value, the constriction detection reference value Vtn for detecting constriction is reduced and, when the counter value reaches the plus reference value, the constriction detection reference value Vtn is increased. Consequently, since the constriction detection reference value Vtn is made appropriate, the detection precision of the constriction is improved.