PROBLEM TO BE SOLVED: To provide a joined material in which deformation and strain can be reduced, to provide a joint structure thereof, to provide a method of producing the joined material, and to provide the body structure of a traffic transportation means.
SOLUTION: The joined material 3 is used for the body structure of a traffic transportation means such as rolling stock. The joined material 3 is a clad plate with a sandwich structure in which a metal 3a and a metal 3b are joined with a joined material layer 3k. The metal 3a is an aluminum alloy, and the metal 3b is a magnesium alloy. In a state where the joining faces 3i of the metal 3a and the joining faces 3j of the metal 3b are mutually butted, a rotary tool 5 is intruded into the joining faces 3i and 3j shown by the figure under pressing from the side of the metal 3b while being rotated, and is moved along the joining faces 3i and 3j, so that the joining faces 3i and 3j are subjected to friction stir joining. As a result, the joined material 3 can be made long, and further, the joined material 3 reduced in deformation and cracks can be produced.