To provide a friction stir welding material in which the surface can be smoothly finished without producing flashes on the surface of a joined part.

A first joining face 13 is composed of a plurality of first recesses 14 and a plurality of first projections 15 that are provided respectively in the thickness direction of a first joining member 10. A second joining face 23 is composed of a plurality of second projections 25 and a plurality of second recesses 24 that are provided respectively in the thickness direction of a second joining member 20. As a result, when the first and second joining faces 13, 23 are abutted on each other, a relative difference in level generated in these joining faces 13, 23 can be reduced. When the joined part of the first and second joining faces 13, 23 is friction-stir welded, the surfaces 11, 21 (rear faces 12, 22) of the joined part of the first and second joining faces 13, 23 can be smoothly finished.