Abstract: Provided is an interference avoiding method in a mobile communication system. A base station detects a preamble signal of another base station during an initial setting process or a time frame of a downlink transmission section to detect an adjacent interference base station or receive a report of information on the adjacent interference base station detected by a mobile station from the mobile station. When an adjacent interference base station is detected, the base station sets a common bandwidth from among the entire usage bandwidth as an interference avoiding bandwidth according to a defined rule. The base station allocates a subchannel in the interference avoiding bandwidth to a mobile station in a cell edge area adjacent to a cell of an interference base station.