PURPOSE: To achieve automatic identification between obstructive apnea and central apnea by extracting information for identification between the obstruc tive apnea and the central apnea with a very simple device and further, based on the results of the extraction.

CONSTITUTION: An analog signal processing section 2 is provided to generate a pulse wave signal by receiving light transmitted through an organism or reflected therefrom after its irradiation from a light source and a pulse wave base line analog signal processing section 9 to extract a changing portion of the base line of the pulse wave signal generated. A master microcomputer 6 is provided and performs an identification between the obstruction apnea and the central apnea based on the changing portion of the base line extracted.