To investigate the recycling of coffee grounds (CGs), the surfaces of CGs were modified with CaCl2 solution, and the adsorption mechanism of NO3--N and NO2--N on these surfaces was evaluated. Maximun adsorption of NO3--N and NO2--N was observed with CGs carbonized at 600 degrees C (CG600), and the amounts adsorbed increased with temperature, at the time of adsorption, reaching equilibrium after 24 h. The amount of chloride ions eluted from CG600 increased with the amount of NO3--N and NO2--N adsorbed. The adsorption isotherms of NO3--N and NO2--N were fitted by the Freundlich and the Langmuir equations. These results indicated that NO3--N and NO2--N were adsorbed onto CG600 by ion exchange. CGs treated with CaCl2 solution can be utilized for the removal of NO3--N and NO2--N from drinking water.