Friction stir welding device and friction stir welding method

A friction stir welding device comprising:

• a friction stir welding tool provided with a non-rotatable fixed shoulder on an outer periphery on a proximal end side of a rotationally drivable probe;
• a moving unit which relatively moves the friction stir welding tool to a welding portion between workpieces in a direction along the welding portion;
• a control device of the moving unit;
• and
• a filler supply unit which supplies, during friction stir welding of the welding portion, a filler to a stirring region, wherein the stirring region is stirred by the rotationally drivable probe,
• wherein the welding portion between the workpieces is a corner portion,
• the non-rotatable fixed shoulder has two workpiece facing surfaces disposed opposite to surfaces of the workpieces on both sides of the welding portion, and
• the control device is programmed to hold the non-rotatable fixed shoulder such that a gap between an entirety of the two workpiece facing surfaces of the non-rotatable fixed shoulder and the surfaces of the workpieces is formed, and the entirety of the two workpiece facing surfaces are parallel to the surfaces of the workpieces, while the rotationally drivable probe is immersed into the welding portion and relatively moves with respect to the workpieces.