To provide a method for synthesizing a single crystal diamond covering a large area by specifying a face direction of the generated diamond nuclei on a single crystal preform plate and synthesizing while charging an electric current in the surface of the preform in a gas phase synthetic method.

This method for synthesizing a diamond is to perform a diamond synthesis on a silicon preform plate 10 while charging an electric current between electrodes 12, 14, so as to grow the [100] direction of the nuclei 18 of the synthesized diamond along the [100] direction in the surface of the silicon preform plate, to form the nuclei 18 having the same surface direction with the silicone preform plate 10. Since the electric current is to help the directional growth of the nuclei 18 in the initial period of the growth, there is no need to charge the current after the formation of nuclei 18. Even by using [110], [111] silicon preform plate, it is possible to make the directional growth of the nuclei by charging the electric current, and even by charging the current in the direction of [110], [111], [112], it is possible to form the diamond nuclei in the same surface direction of the base preform plate. As the base preform plate, even by using a β-SiC, it is possible to make a hetero epitaxial growth of the diamond, and further, even a base preform plate of an alloy consisting of Ni, Cu as main components can be used.