The invention is intended to establish means for manufacturing MB 2 single crystals and to provide a useful superconductive material (wire rod and so forth) taking advantage of anisotropic superconductive properties thereof. A mixed raw material of Mg and B or a precursor containing MgB 2 crystallites, obtained by causing reaction of the mixed raw material of Mg and B, kept in contact with hexagonal boron nitride (hBN), is held at a high temperature in the range of 1300 to 1700°C and under a high pressure in the range of 3 to 6 GPa to cause reaction for forming an intermediate product, thereby growing the MB 2 single crystals having anisotropic superconductive properties via the intermediate product. The single crystals have features such that, depending on a direction in which a magnetic field is applied thereto, an irreversible magnetic field strength becomes equivalent to not less than 95% of a second magnetic field strength, so that adjustment of crystal orientation thereof results in production of a superconductive material excellent in property. Further, it is useful in effecting growth of the single crystals to cause a reducing agent such as Mg and so forth to coexist at the time of the reaction, or to provide a temperature gradient in melt occurring in the course of the reaction.