Friction stir welding device and friction stir welding method

A friction stir welding device comprising:

• a table comprising a placement surface configured to have a workpiece placed thereon and that is rotatable about a table rotation axis intersecting the placement surface;
• a tool holder that is movable relative to the table in a direction along the placement surface and that is rotatable about a holder rotation axis parallel to the table rotation axis, the tool holder comprising a machining shaft configured to rotate about a tool rotation axis intersecting the holder rotation axis;
• a welding tool mounted on a tip of the machining shaft, the welding tool being supported by the tool holder and that is configured to rotate about the tool rotation axis intersecting the holder rotation axis, the welding tool comprising a machining portion, which is a tip of the welding tool, and which is disposed at a location on the holder rotation axis;
• and
• a control device configured to control an operation of each of the table, the tool holder, and the welding tool,
• the control device having a biaxial operation mode in which the welding tool in a rotating state is pressed against a welding portion of a side surface of the workpiece, the welding tool is relatively moved along the welding portion by rotating the table, and the tool holder is rotated so that the welding tool is directed in a normal direction of the welding portion.