Provided are a universal blind mode detector capable of universally detecting not only various orthogonal frequency division multiplexing (OFDM) communication services but also non-OFDM communication services, and a fast Fourier transform (FFT) mode detector, a guard mode detector, and a memory sharing structure of the universal blind mode detector, and a method of detecting a universal blind mode. The universal blind mode detector includes a radio frequency (RF) tuner converting a received signal into a baseband frequency signal, an automatic gain control (AGC) unit which is connected to the RF tuner and determines existence of a communication service by referring to a received signal strength indication (RSSI), a communication service mode detection unit determining of which scheme a communication service mode signal is if the AGC unit determines that there is the communication service, and detecting the communication service mode signal, and a channel decoding unit detecting the detected signal.