A nose mask for applying an anesthesia gas to a laboratory animal in a casing means includes an anesthesia tube, an outer wall which is disposed outside the anesthesia tube to form a space therebetween and an anesthesia recovery system having an anesthesia recovery port open to the space. The anesthesia tube includes an anesthesia supply section which opens to an wall of the anesthesia tube so that the anesthesia is applied to the laboratory animal by inserting the nose of the laboratory animal, an anesthesia introducing section for introducing the anesthesia gas to the anesthesia tube, and an anesthesia discharging section for discharging the anesthesia gas from the anesthesia tube.
