PURPOSE: To improve processability in a complex condition by adding 10-2000ppm of beryllium to aluminium or aluminium alloy so as to be composite with a niobium material.

CONSTITUTION: By using a material in which 10-2000ppm of beryllium is added to aluminium or aluminium alloy, as a material to be composite with a niobium material, processability in a complex condition is radically improved. When the amount of beryllium is not less than 10ppm, the effect of addition begins to work, however, when it exceeds 2000ppm, processability is deteriorated. When processability in a complex condition is improved, inhomogeneous deformation between niobium and aluminium is reduced, and a homogeneous filament is formed. It is thus easy to determine the optimal ratios of niobium and aluminium, and Nb3Al of good stoichiometry is formed. An Nb3Al superconducting wire of high critical magnetic field, and of high critical current density in a high magnetic field, can be obtained.