Abstract: A method and apparatus for welding sectional members onto a large-format aluminum structural component using laser beams is especially applicable for welding stringers onto cylindrically or spherically pre-curved fuselage skin components in the construction of aircraft. The apparatus includes an adjustable support arrangement for supporting the large-format structural component, a roller guide and clamping system by which the sectional member, after it has been prepositioned, is guided by a computer numeric control (CNC) system and fixed onto the structural component, and a laser guide system that simultaneously directs two laser beams from two opposite sides of the sectional member onto a weld point along a joint seam between the sectional member and the structural component. The method and apparatus are applicable and readily adaptable with high flexibility to a great variety of geometries of the components to be welded, because the laser guide system is not coupled to the roller guide and clamping system.