The structures of the B6O samples prepared by oxidizing boron with ZnO at temperatures of 1350-1500°C in an argon atmosphere have been refined by the Rietveld method. The B6O samples were found to contain an amorphous phase from their X-ray diffraction profiles in addition to B6O diffraction peaks. The results indicate that the B6O samples, space group R¯3m, no.166, a hex = 0.5367(1) nm and c hex = 1.2328(2) nm in the hexagonal unit cell, have oxygen deficiencies with 0.76(6) oxygen occupancy. A radial distribution function method applied to an extracted portion of the amorphous phase, suggests that each amorphous phase has nearly similar short-range order structure to that of the α-tetragonal boron type rather than to those of any other related boron phases.