A slab laser includes cooled, mutually parallel electrodes having a given thickness. The electrodes have flat surfaces facing each other and defining a discharge chamber therebetween for containing a gas to be pumped, and the electrodes have flat surfaces facing away from the discharge chamber. Each of the electrodes has a plurality of sections being spatially separated from one another over at least a portion of the given thickness of the respective electrode. The electrodes are supported in such a way that movements of the flat surfaces facing away from the discharge chamber being caused by thermal expansion are opposed by only a negligible mechanical resistance.