PURPOSE: To automate and speedup submerged welding by automatically changing/controlling the welding condition so as to obtain a welding leg length corresponding to a base metal to be welded when continuous welding of linear/ curved welding place is executed in a base metal to be welded.

CONSTITUTION: The device is provided with a setting value inputting means 21 to input the discrete setting value for a base metal 1 to be welded, the setting value inputted in the setting value inputting means and welding actual value are compared, by this comparing signal, for the base metal to be welded in which a plate thickness (t) of a base metal to be welded along the welding running direction is irregularly changing from t1 to t2, in order to obtains a welding leg length s1-s2 corresponding to a plate thickness at welding place, a relative running speed between a welding bar 7 and base metal 1 to be welded, welding bar feed speed, arc voltage and arc current are automatically controlled.