Friction stir welding tool

A friction stir welding tool that welds welding target materials to each other, the friction stir welding tool comprising:

• a shank coaxially connected to a rotating member;
• a first spiral portion integrally formed with the shank, and having a first spiral surface extending in a spiral shape around an axis extending coaxially with the rotating member so as to approach the axis as being separated from the shank in an axial direction;
• a second spiral portion integrally formed with the first spiral portion, and having a second spiral surface extending in a spiral shape in a direction opposite to the first spiral surface around the axis so as to be separated from the axis as being separated from the first spiral portion in the axial direction on a side opposite to a shank side;
• and
• a heat receiving portion integrally extending from the second spiral portion on a side opposite to a first spiral portion side and configured to receive heat from the second spiral portion.