PURPOSE: To execute automatic profile welding which is simple and practical, and has reliability, by detecting a position of a welding torch against a weld line from comparison of values of both the left and right ends of oscillation, and controlling a position of the torch.

CONSTITUTION: Wire extension LE and arc length LA are derived by providing a welding current, a wire feed speed, and voltage between a chip 3 and an work to be welded 12, to a computer 24, and LE+LA and a set value between the chip and the work to be welded are compared by a program of the computer 24. A result of comparison is outputted to a motor control power source 36, and a welding torch 1 is moved up and down by an up-and-down moving device 15. Also, a position of the welding torch 1 is controlled by driving a motor 16 and also moving a left and right moving device 17 to the left and right. In this regard, the position of the torch 1 is detected by an oscillation position detector 29, and is inputted to the computer 24 through an A/D converter 30. In this way, a distance between the chip 3 and the work to be welded 12 is kept constant, and also, even in case when the weld line and the groove line are shifted, the welding device corrects a track by itself.