A friction welded joint structure includes friction welded dissimilar first and second metallic materials. The first metallic material has a rigidity greater than the second metallic material. The angle of the first metallic material to a free edge of the first metallic material, at an end portion of a joined surface between the first and second metallic materials, is greater than or equal to 120 degrees or in the range of from 55 degrees to 85 degrees. A reaction layer between the first and second metallic materials is more than zero and less than or equal to 20 &mgr;m. The first metallic material is copper. The second, which has the smaller rigidity, is aluminum.