A gas-shielded arc welding apparatus automatically welds materials to be welded, such as rails or shape steel. The apparatus includes a gas-shielded chamber and a pair of side backing plates arranged within the chamber whereby the whole weld zone of the materials is gas shielded and a welding nozzle and shielding gas outlets are separated from each other. The apparatus also includes a welding apparatus proper and a control unit thereby performing the welding in a fully automatic manner.
