Each of a plurality of electroencephalographs is adapted to measure electroencephalograms of a patient and to be connected to a communication network. Each of the electroencephalographs is operable to analyze the electroencephalograms to generate electroencephalogram information. Each of a plurality of cameras is adapted to monitor a state that the patient is subjected to the electroencephalogram measurement to transmit the monitored state as image information to associated one of the electroencephalographs. A central control monitor is connected to the communication network and operable to simultaneously displaying the electroencephalogram information and a part of the image information which are transmitted from each of the electroencephalographs via the communication network.