Abstract: The present invention provides a method for determining sleep stages of an examinee, including detecting signals of the examinee with a biosignal detector, calculating a signal strength deviation value that indicates deviation of a signal strength of the detected signals, and determining a sleep stage by using the signal strength deviation value or a value of a plurality of values based on the signal strength deviation value as an indicator value.

Abstract: A person who is elderly, requires care, or an inpatient who is under the care by his or her family members, a nursing care worker, or a nurse in a hospital or medical institution must be monitored constantly, however the caregiver cannot be in attendance on the patient all the time. A biosignal intensity measuring method is provided to solve the above problem. According to the measuring method, output signals from a noninvasive sensor, which detects biosignals from a lying subject, are amplified and noises other than the biosignals are attenuated via a signal amplifying/shaping unit, and the amplified signals are controlled by an automatic gain control (AGC) unit to have sizes within a prescribed range, then parameters acquired by signal gains in a control circuit upon carrying out automatic gain control are output as the output signal intensity of the biosignals to calculate biosignal intensity. A bedding state monitoring method is also provided.