the object of this invention is to provide an extremely simple device to extract information to distinguish between obstructive apnea and central apnea and which performs this operation automatically based on the extracted information . the device is equipped with analog signal processor 2 for generating pulse wave signals based on light received from a light emitting means and passing through or reflecting off living tissue ; pulse wave base line analog signal processor 9 for extracting change components of a base line of the generated pulse wave signal ; and master microcomputer 6 for distinguishing between obstructive apnea and central apnea on the basis of the extracted pulse wave base line change components .