Recently, some harmful compounds and bacteria have been detected from tap water. Particularly, the nitrite nitrogen causes methemoglobinemia and cyanosis for infants. In this study, the surfaces of coffee grounds were carbonized by microwave and carbonaceous materials were produced. The specific surface area of the coffee grounds did not change by carbonization, while the base consumption decreased. Moreover, we estimated the extent of the adsorption of nitrite nitrogen onto the coffee grounds in terms of its removal from tap water. The adsorption mechanism of nitrite nitrogen onto coffee grounds would be monolayer adsorption, because the adsorption isotherms fitted to Freundlich or Langmuir equations. It is suggested that the adsorption of nitrite nitrogen onto coffee grounds is related to the phenolic hydroxyl and carboxyl groups. The coffee grounds thus can be utilized for the removal nitrite nitrogen from tap water.