An aluminium diffuser was developed by grinding the aluminium plates with free abrasive, and using a vacuum-deposited layer of pure aluminium. The instruments used for bidirectional reflectance distribution function (BRDF) measurements were established. The BRDF and hemispherical reflectance of the aluminium diffuser was measured. The total hemispherical reflectance of the aluminium diffusing plate is 49% at 315 nm. At normal incidence, the BRDF of the ground aluminium changes about 11% over 15°～40° scattering angle range.