Abstract: A joining device for joining a component to a workpiece. The device includes a component holder which moves the component along an axis in a first direction towards the workpiece in order to connect the component to the workpiece, and has a protective gas feed in order to carry out a welding process in a protective gas atmosphere. During the welding process the protective gas is discharged essentially in a second direction which is opposed to the first direction. An elastic sealing sleeve including folding bellows is arranged in relation to the component holder in such a way that a welding space, which is bounded by the workpiece, the component holder, the component and the sealing sleeve and through which the protective gas flows, is sealed off from the external surroundings during the welding process so that the protective gas can escape only in the second direction.