An electroencephalogram signal processing method includes a recording step, a retrieving step, a removing step and a synthesizing step. The recording step retrieves EEG signal components of a testee via a plurality of electrodes, wherein the EEG signal components serve as an input signal. The retrieving step filters the input signal to obtain a predetermined frequency band signal, and subtracts the predetermined frequency band signal from the input signal to obtain a difference signal. The removing step performs an independent component analysis operation between the difference signal and a separating matrix to obtain an analysis signal, generates a separating pseudo inverse and an independent analysis signal, and performs a matrix operation between the separating pseudo inverse and the independent analysis signal to obtain a corrected signal. The synthesizing step adds the corrected signal and the predetermined frequency band signal together to obtain an output signal.