A method of detecting an illegal broadband radio signal, the method comprising: receiving, by a reception unit, a surrounding radio signal at a place where an illegal radio signal is to be detected; generating, by a detection unit, reference frequency information by configuring a reference multi-spectrum table in such a way as to generate a basic resolution spectrum by extracting a signal of a preset frequency band at a basic resolution from the received surrounding radio signal and to generate a multiple resolution spectrum by extracting the signal of the preset frequency band at a resolution of a positive integer multiple of the basic resolution from the received surrounding radio signal; and generating, by the detection unit, detection frequency information by configuring a detection multi-spectrum table in such a way as to generate a basic resolution spectrum by extracting a signal of the preset frequency band at the basic resolution from a detection radio signal detected in the place where an illegal signal is to be detected and to generate a multiple resolution spectrum by extracting the signal of the preset frequency band at the resolution of a positive integer multiple of the basic resolution from the detection radio signal; characterized by identifying, by a determination unit, whether a signal intensity value greater than a corresponding signal intensity value of the basic resolution spectrum of the reference multi-spectrum table is present in the basic resolution spectrum of the detection multi-spectrum table by comparing signal intensity values of the basic resolution spectrum of the detection multi-spectrum table with corresponding signal intensity values of the basic resolution spectrum of the reference multi-spectrum table, when it is identified that a signal intensity value greater than a corresponding signal intensity value of the multiple resolution spectrum of the reference multi-spectrum table is present in the multiple resolution spectrum of the detection multi-spectrum table; and identifying, by the determination unit, that an illegal radio signal has been detected in the detection radio signal when it is identified that a signal intensity value greater than the corresponding signal intensity value of the basic resolution spectrum of the reference multi-spectrum table is not present in the basic resolution spectrum of the detection multi-spectrum table by comparing the signal intensity values of the basic resolution spectrum of the detection multi-spectrum table with the corresponding signal intensity values of the basic resolution spectrum of the reference multi-spectrum table. receiving, by a reception unit, a surrounding radio signal at a place where an illegal radio signal is to be detected; generating, by a detection unit, reference frequency information by configuring a reference multi-spectrum table in such a way as to generate a basic resolution spectrum by extracting a signal of a preset frequency band at a basic resolution from the received surrounding radio signal and to generate a multiple resolution spectrum by extracting the signal of the preset frequency band at a resolution of a positive integer multiple of the basic resolution from the received surrounding radio signal; and generating, by the detection unit, detection frequency information by configuring a detection multi-spectrum table in such a way as to generate a basic resolution spectrum by extracting a signal of the preset frequency band at the basic resolution from a detection radio signal detected in the place where an illegal signal is to be detected and to generate a multiple resolution spectrum by extracting the signal of the preset frequency band at the resolution of a positive integer multiple of the basic resolution from the detection radio signal; characterized by identifying, by a determination unit, whether a signal intensity value greater than a corresponding signal intensity value of the basic resolution spectrum of the reference multi-spectrum table is present in the basic resolution spectrum of the detection multi-spectrum table by comparing signal intensity values of the basic resolution spectrum of the detection multi-spectrum table with corresponding signal intensity values of the basic resolution spectrum of the reference multi-spectrum table, when it is identified that a signal intensity value greater than a corresponding signal intensity value of the multiple resolution spectrum of the reference multi-spectrum table is present in the multiple resolution spectrum of the detection multi-spectrum table; and identifying, by the determination unit, that an illegal radio signal has been detected in the detection radio signal when it is identified that a signal intensity value greater than the corresponding signal intensity value of the basic resolution spectrum of the reference multi-spectrum table is not present in the basic resolution spectrum of the detection multi-spectrum table by comparing the signal intensity values of the basic resolution spectrum of the detection multi-spectrum table with the corresponding signal intensity values of the basic resolution spectrum of the reference multi-spectrum table.