An eyeglass-type electroencephalogram interface system is worn on the head of a user. The system includes: an output section for presenting a visual stimulation to the user an ear electrode portion disposed at a position coming in contact with an ear of the user when the system is worn a facial electrode portion disposed at a position coming in contact with the face below a straight line connecting an external canthus and an internal canthus of an eye of the user, such that the mass of the system is supported at the position, when the system is worn and an electroencephalogram measurement and determination section for measuring an event-related potential on the basis of a potential difference between the ear electrode portion and the facial electrode portion based on the visual stimulation being presented by the output section as a starting point.
