A radio relay apparatus, a monitoring apparatus, and a method of determining an identification code of the radio relay apparatus enabling rapid formation of a radio communication area. The radio relay apparatus receives the base station identification code from a base station, determines a temporary identification code based on the received base station identification code, and transmits the temporary identification code to the monitoring apparatus. When the received temporary identification code is different from the formal identification codes of other radio relay apparatuses, the monitoring apparatus transmits directly the temporary identification code to the radio relay apparatus; when the received temporary identification code is the same as the formal identification code of a radio relay apparatus, the monitoring apparatus determines an identification code different from the temporary identification code and transmits the determined identification code to the radio relay apparatus. The radio relay apparatus determines the received identification code as a formal identification code of the radio relay apparatus. Then, the radio relay apparatus starts operations using the formal identification code.