PURPOSE: To enable even a double V groove to be welded by means of two layers of one run continuous welding on the high alloy side, in the butt welding of a clad steel, and to remarkably improve the efficiency of welding execution.

CONSTITUTION: In this butt welding method for a clad steel, the abutting shape of the clad steel is a double V and in welding a high alloy steel 2 side, one run continuous welding is performed for the two layers, by combining GMAW method for the groove of a low alloy steel with a wire delta arranging type SAW method for the remaining groove of a high alloy steel.