The invention relates to a device and a method for changing the welding direction of the welding shoulder of a system for a friction stir welding process virtually without delay when required by the geometric arrangement of the joint partners to be welded or by a material unevenness, having the following method features: a) a main part (1) with a horizontally movable bridge support (5) has a friction welding head (12) which can be vertically adjusted together therewith and which has a pin receiving area (13) for mounting and driving a welding pin tip (14), wherein the welding shoulder (18) has a welding shoulder receiving area (17) which is supported at multiple points, and b) the welding shoulder receiving area (17) can be adjusted to any angle of attack relative to the joint partners by means of different push-pull rods (16) during the welding process.