Abstract: A process and a device for the laser welding of plates (3, 4) located next to each other, which are held together with a movable clamping device (5). The feed path is measured during the closing of the clamping device (5), the thickness of the plate stack (3, 4) is calculated from this, and sent out. The welding energy is set according to the measured thickness of the plate stack. This can be achieved with an automatic control unit, which automatically sets the welding energy source (11). The welding head (2), designed as a laser focus, may be integrated within the clamping device (5) and may be fed together with same.