To provide a traffic monitoring apparatus capable of accurately determining the number of objects present in an area under surveillance without being affected by the difference in arrangement of those objects. \u201d The communication apparatus on the reception side and a communication apparatus on a transmission side discard a part of pieces of the common information according to public error correction information. A method of functionalizing a carbon nanotube includes heating a fluorinated carbon nanotube urea, thiourea, or guanidine.