Patent ID: 7766214

Claim:
A friction stir welding method of inserting a tool having a pin-shaped probe protruding therefrom into member to two or more weld materials in a state of being rotated, and said tool is moved in a state of being rotated, thereby welding the two or more weld materials in accordance with a friction stirring, wherein a cavity is provided in a part of a weld portion of said two or more weld materials, an embedded member is provided in said cavity, and said two or more weld materials are welded by the friction stirring along the embedded member and at a position coming into contact with the embedded member, wherein, prior to said inserting, (a) overlapping one of the two or more weld materials with another of the two or more weld materials, each of said one and said another of the two or more weld materials having cavity portions having semicircular cross-sectional shapes, such that when overlapped the one and another of the two or more weld materials form the cavity, the cavity having a circular cross-section, and (b) embedding the embedded member in the cavity having the circular cross-section.