An implant structure for medical use is provided. The implant structure includes an implant body and a nailing portion. The implant body and the nailing portion are integrally formed as a unitary structure to thereby prevent separation between the implant body and the nailing portion which might otherwise occur after long use. The nailing portion has a bone-contacting surface with at least one barb unit formed thereon for enhancing the bonding of the implant structure and a bone, preventing the implant structure from loosening, and extending the service life of the implant structure.