An electroencephalogram waveform is displayed in a first display area in a real time manner such that a direction indicating lapse of time is oriented horizontally. A second display area is provided adjacent to the first display area in which CSA or DSA derived from the electroencephalogram waveform, which has been displayed in the first display area, is consecutively displayed. A pulse waveform is displayed in a third display area in a real time manner such that a direction indicating lapse of time is oriented horizontally. A fourth display area is provided adjacent to the third display area so that the pulse waveform, which has been displayed in the third display area, is consecutively displayed in a compressed form. The electroencephalogram waveform in the first display area and the pulse waveform in the third display area are displayed synchronously with each other. The CSA or the DSA in the second display area and the compressed pulse waveform in the fourth display area are displayed synchronously with each other.