Hydrogenation of nitrate in water over Pt-promoted nickel catalysts has been studied with a liquid - gas flow reaction system. While nickel powder obtained from Ni-Al alloy showed an activity for hydrogenation of nitrate (200 ppm) at the initial stage at 333 K, it deactivated rapidly during the reaction. Contrary to this, 1 wt% Pt-promoted nickel exhibited an extremely high activity to NH3 and stability. The reaction rate on 1wt% Pt-Ni was nearly proportional to the concentration of nitrate up to 5000 ppm, showing that this catalyst is applicable to the treatment of wastewater containing concentrated nitrate. ICP analysis showed that both the platinum and nickel were not dissolved during the reaction. XPS measurement revealed that platinum played an important role in suppression of the oxidation of the nickel surface to retain the active Ni-0 surface.