PURPOSE: To provide a welding method by which a laminated sheet metal can be subjected to a butt welding to a middle thick plate without a defect, surely, and also, with satisfactory workability.

CONSTITUTION: A stay metal 4 and a strap 3 are arranged in the outside of the lower face of a sheet metal laminated body 1, and in the outside of the upper face, respectively, pressure force is allowed to work on at least one of this stay metal 4 and the strap 3, and the sheet metal laminated body 1 is subjected to pressure welding, by which a multi-layer body 6 is formed. By chamfering the end face part of this multi- layer body 6 by a grinder, the groove inclined surface 7 is formed. After eliminating the stay metal 4 from the multi-layer body 6, a lower side backing plate 8 is arranged in a state that it is protruded by 2-3mm from the end face of the sheet metal laminated body 1. In the inclined groove surface 7, the upper and the lower backing plates 3, 8 and the sheet metal laminated body 1 are tacked and fixed in a pitch of ≤10mm. After tacking, the end face of the laminated body 1 and the end face of a middle thick plate 12 are butted and arranged, and its weld line part is subjected to the multi-layer welding after a first layer is subjected to a penetration welding by TIG welding.