Very hard diamondlike carbon films have been prepared with the aid of an ionized deposition technique. The growth mechanism of films deposited in the presence of methane gas is discussed. The properties of these carbon films are as follows: The concentration of hydrogen atoms contained in the films is almost negligible. Micro‐Vickers hardness changes depended largely on the deposition conditions, but some of the values obtained were larger than that of sapphire. The 111, 220, and 311 reflections can be observed clearly in the electron diffraction patterns. Moreover the crystal structure obtained from these rings is very close to that of diamond.