A joined structure has high strength, which is used for manufacturing a joint made from different metal materials. In the joined structure in which the different metal materials are joined, a reaction product layer to be generated on the joined interface is set to have a thickness of 0.5 &mgr;m or less. Moreover, the reaction product layer is allowed to intermittently exist on the joined interface. Furthermore, the reaction product layer contains a base material crystal consisting of base material atoms of 90 atom % or more on the joined interface.