Abstract: A method and a device for manufacturing a grid for use in a nuclear reactor fuel assembly. A grid whose component parts are to be mutually welded is placed in a holding frame having passages for access to points to be welded on two major faces and on the sides. The frame containing the grid is gripped with a device in a chamber where an inert gas atmosphere is generated. Welding is carried out on one face of the grid at a time using a laser beam penetrating from outside the chamber and the welding operations are repeated on the other faces. During welding on one face, the laser beam is moved in two mutually orthogonal directions while the frame is held stationary. The apparatus may include two chambers each with a gripping device, one for welding the two major faces and the other for welding the sides.