An inert gas containing carbon dioxide and ammonia and separated from a urea synthesis effluent under urea synthesis pressures is brought into contact with an absorbent along with unreacted carbon dioxide and ammonia separated in high pressure distillation at a pressure of from 10 to 25 kg/cm2G to absorb substantially all of the carbon dioxide and the major portion of the ammonia, and is cooled to be separated from the resulting liquid ammonia and then discharged. The inert gas can be treated with little or no danger of explosion by the above method.