PROBLEM TO BE SOLVED: To provide a non-constraint apnea detection system that realizes low-cost and high-precision analysis of a breathing state without binding a subject by generating a high frequency sound upon attaching an expiratory sound generator having a silent whistle to the nose and/or the mouth and by collecting the sound, and to provide a method therefor and a program therefor.SOLUTION: A non-constraint apnea detection system comprises: an expiratory sound generator 2 that has a silent whistle capable of generating a high frequency sound of 5 kHz or higher and is attached to the nose or the mouth a sensor 3 that can receive a breathing sound generated from the expiratory sound generator 2 or from the nose or the mouth a frequency analysis part 5 that analyzes a spectrum of the breathing sound a spectrum envelope analysis part 6 that analyzes a spectrum envelope of the spectrum to obtain a spectrum envelope curve and a breathing state analysis part 7 that determines an apnea state when the spectrum envelope cuve has no maximum points or when intensity in the frequency giving a peak point among the maximum points does not exceed a desired threshold.
