Highly pure, high-density rhombohedral polycrystalline boron nitride substantially comprising rhombohedral crystals and having a three-fold axis of symmetry (an axis parallel to axis c according to hexagonal representation) oriented to one direction, which can be obtained in an arbitrary mass or thin film form by a chemical vapor deposition process of introducing a boron source gas and a nitrogen source gas and, optionally, a diluting and carrier gas into a reactor provided with a heated base to deposit boron nitride on the base, while providing a nitrogen source gas- and/or a carrier gas-diffusing layer around the heated base. The resulting boron nitride is extremely useful as semiconductors, crucibles for melting, various high-temperature jigs, high-frequency insulators, microwave transmitting apertures, and boron source for semi-conductors and, in addition, optimal as a precursor of high-pressure phase cubic boron nitride.