Abstract: An inplant material for a living body hard tissue which is constructed by forming a core of a carbon material having a smooth and high hardness surface, an excellent mechanical strength against bending and compressing strengths, and non-impregnable to blood, lymph or the like and further forming a porous layer having a thickness of 100 microns or larger, preferably 100 microns or large on the surface of the core. This porous structure of the implant material is very important to smoothly and rigidly bond the material to a living body and is devised to produce the state that a collagen fiber newly produced in the boundary between the living body and the implant material is intruded into the porous tissue of the surface of the implant material and mutually interchanged, and a process for producing the same. Thus, the implant material has a smooth and high hardness surface, an excellent mechanical strength against bending and compressing strengths, and being non-impregnable to blood, lymph or the like.