Hot-pressed B(4)C is found to have a high normal reflectance in the extreme-UV spectral region above 49 nm. This reflectance is comparable with or higher than chemical-vapor-deposited SiC in the spectral region from 49 to 92 nm. Reflectance measurements as a function of the angle of incidence yielded the optical constants of B(4)C in the spectral range 49-121.6 nm.