Provided is a method and apparatus for assigning a frequency in an environment where an incumbent system exists. In a frequency environment where the incumbent system exists, a frequency resource management may be smoothly performed using a plurality of frequency sets classified based on a utilization state of each sub-frequency resource. When a frequency sharing system using the same radio access technology (RAT) as a frequency sharing system to be assigned with a frequency resource exists, it is possible to reduce overhead for frequency sharing by priorly assigning a corresponding frequency resource to the frequency sharing system to be assigned with the frequency resource.