The invention provides a friction-welded part featuring easy design as well as a method of producing said part. The friction-welded part 1 is produced by friction-welding a first member 10 and a second member 20 together. The first member 10 is made of an aluminum alloy material, having a uniform cross-section portion 11 whose cross-sectional shape and size are not changed. The second member 20 is made of an aluminum alloy material, having a uniform cross-section portion 21 whose cross-sectional shape and size are not changed. According to the invention, the uniform cross-section portions 11 and 21 are friction-welded together to form the part 1. A heat affected zone “H” caused by friction welding is formed only in the uniform cross-section portions 11 and 21. The uniform cross-section portion 11 of the first member 10, and the uniform cross-section portion 21 of the second member 20, respectively, have a cylindrical shape, preferably having the same sectional dimension.