Structural changes occurring in the crystalline element selenium upon high-energy ball milling has been studied. Milling experiments have been performed at the ambient temperature and at a cryogenic temperature of -100 degrees C, respectively. The final milling products under both conditions were found to be a fully amorphous phase after several hours of mechanical milling. Calorimetric evidences indicate that during cryogenic-temperature milling amorphization procedure is faster than that at ambient temperature. Our experimental results suggest that amorphization of the crystalline element selenium is driven by defects created by frequent mechanical deformation.