A study has been made of surface properties of carbon materials modified by ion beams. Substrates used were natural diamonds, glass-like carbon plates and polymer sheets. Ion species were chemically-active elements such as C, N and O, inert gas elements such as He, Ne and Ar, and metallic elements such as Cr and Ti. It was found that diamond becomes electrically conductive in ion implanted layers, which are amorphous or graphite-like structures. Electrical conductivity depends on implanted species, doses and target temperatures. It was found that glass-like carbon consisting of graphite and disordered graphite becomes amorphous due to ion beam bombardment. Amorphization causes the wear resistance to improve. The electrochemical properties changes depending on implanted species. The wear resistance and electrochemical properties depended on the target temperature during ion implantation. Ion beam bombardment to polymers has been carried out to control the electrical conductivity, cell adhesion and bio-compatibility. The electrical conductivity of polyimide films increases as the dose increases. The saturated sheet resistivity of implanted layers depends on ion species, dose and dose rate. It was found that the cell adhesion can be controlled by ion beam bombardment. The results were used in the fields of clinical examinations. In summary, ion beam bombardment to carbon materials is useful to control the carbon structures and surface properties depending on ion implantation conditions.