A frequency band coordination method in a cognitive radio system comprising: a control channel determination step of determining a frequency band to be used as a control channel; a data channel determination step of communicating a frequency use status around a transmitting node and a receiving node through said control channel and determining a frequency band to be used as a data channel; and a channel changing step of communicating a frequency use status around a transmitting node and a receiving node during communication through said control channel, and changing the frequency band used as the control channel or the data channel when the control channel being used or the data channel being used has become unusable or is expected to become unusable; wherein said control channel determination step comprises: a step of detecting, by each of the transmitting node and the receiving node, usable frequency bands in a specific frequency range that are suitable for the control channel; a step of transmitting, by the transmitting node, a connection request using frequency bands usable by itself; a step of transmitting, by the receiving node, an acknowledgement response in frequency bands in which the receiving node has received the connection request; and a step of selecting, by the transmitting node, any one of frequency bands in which the transmitting node has received the acknowledgement response, as the control channel; and wherein the transmitting node and the receiving node have a common hash function, and in the step of detecting usable frequency bands in the control channel determination step, they obtain location information of themselves and time information, and the frequency range over which the detection is to be performed is narrowed down based on the location information and the time information using the hash function. a control channel determination step of determining a frequency band to be used as a control channel; a data channel determination step of communicating a frequency use status around a transmitting node and a receiving node through said control channel and determining a frequency band to be used as a data channel; and a channel changing step of communicating a frequency use status around a transmitting node and a receiving node during communication through said control channel, and changing the frequency band used as the control channel or the data channel when the control channel being used or the data channel being used has become unusable or is expected to become unusable; wherein said control channel determination step comprises: a step of detecting, by each of the transmitting node and the receiving node, usable frequency bands in a specific frequency range that are suitable for the control channel; a step of transmitting, by the transmitting node, a connection request using frequency bands usable by itself; a step of transmitting, by the receiving node, an acknowledgement response in frequency bands in which the receiving node has received the connection request; and a step of selecting, by the transmitting node, any one of frequency bands in which the transmitting node has received the acknowledgement response, as the control channel; and wherein the transmitting node and the receiving node have a common hash function, and in the step of detecting usable frequency bands in the control channel determination step, they obtain location information of themselves and time information, and the frequency range over which the detection is to be performed is narrowed down based on the location information and the time information using the hash function. a step of detecting, by each of the transmitting node and the receiving node, usable frequency bands in a specific frequency range that are suitable for the control channel; a step of transmitting, by the transmitting node, a connection request using frequency bands usable by itself; a step of transmitting, by the receiving node, an acknowledgement response in frequency bands in which the receiving node has received the connection request; and a step of selecting, by the transmitting node, any one of frequency bands in which the transmitting node has received the acknowledgement response, as the control channel; and wherein the transmitting node and the receiving node have a common hash function, and in the step of detecting usable frequency bands in the control channel determination step, they obtain location information of themselves and time information, and the frequency range over which the detection is to be performed is narrowed down based on the location information and the time information using the hash function.