When a brain fingerprint is detected, a predetermined visual stimuli is output on a screen of a display, causal connectivity formed by unique EEG signals of a subject between two or more brain regions from among a predetermined plurality of brain regions is detected on the basis of the EEG signals of the subject who selectively attends to a part corresponding to a letter or symbol conceived by the subject from among the visual stimuli output on the screen of the display, an activation pattern of causal connectivity between brain regions is recognized on the basis of the detected causal connectivity, and the subject is identified by using the recognized unique activation pattern of causal connectivity between brain regions as a brain fingerprint.
