To provide a high strength connecting rod by applying a friction stirring treatment to proper portions to increase production efficiency and reduce cost.

After the rod body 2 of the connection rod 1 is formed by casting an aluminum alloy, the friction stirring treatment is applied to an area ranging from a part of the surface of a shaft holder part 5 to a part of the surface of a small end part 4 through the surface of a rod part 6. In the connecting rod 1 thus obtained, as compared with the tensile strength of the untreated connection rod, the tensile strength of the treated connection rod is increased by about 60%. As a result, the connecting rod 1 can be formed at a low weight by casting the aluminum alloy while increasing the production efficiency and reducing cost. In addition, the highly strong connecting rod can be provided.