The present invention relates to a bio-adhesive agent comprising a surface-modified hydroxyapatite and its use. More specifically, the present invention relates to a bio-adhesive agent for the adhesion between bone and bone, bone and tissue, bone and cartilage, or bone and tendon, or for the adhesion of a shield between bones or of an artificial joint, which comprises a surface-modified hydroxyapatite as an active ingredient, wherein the surface-modified hydroxyapatite is characterized in that a certain linker compound is covalently bonded to the surface of the hydroxyapatite a method for coating the surface of a metal prosthesis using the surface-modified hydroxyapatite and a metal prosthesis coated with the surface-modified hydroxyapatite obtained by said method.
