Ammonium sulfate is commonly applied on the snow surface of ski runs to maintain the snow condition for the Alpine events. The applied ammonium sulfate possibly causes acidification of soil, deterioration of vegetation and so on. However, discharge processes of the applied ammonium sulfate from snowpack are still unknown. In this study, the discharge characteristics of applied ammonium sulfate were investigated by collecting snow meltwater through a lysimeter (1m2) and measured pH, conductivity, NH4+ concentration, SO42- concentration and δ18O. The applied ammonium sulfate was discharged from the snowpack with little change in quality. In contrast, the snow meltwater was acidified a little bit because of nitrification after application. The applied ammonium sulfate was not absorbed into the snow particles but adsorbed on the surface of the snow particles. Most of ammonium sulfate was thus immediately discharged with snow meltwater. Flow of water in snowpack and the daily variation of snow meltwater quality were affected by the application of ammonium sulfate, because ammonium sulfate lowers the snow temperature and keeps the freezing condition.