FIELD: medicine.SUBSTANCE: group of inventions relates to medicine and can be used for non-invasive determination of superficial and deep sleep stages within the stage of non-rapid eye movement (NREM) sleep. Method of measuring and differentiation of deep sleep stage from superficial sleep stage within subject's NREM sleep stage in intervals of discretisation, includes measurement in each discretisation interval of subject's peripheral pulse signal in the place of subject's body, connected with their large circulation circle； analysis of measured signal of peripheral pulse and application of analysis results to determine whether each discretisation interval is interval of superficial or deep sleep. Analysis of measured peripheral pulse signal includes determination of the following variables: 1) average amplitude and heart rate in measured peripheral pulse signal； 2) scaling coefficient of fluctuation analysis with eliminated trend of amplitude and heart rate in measured peripheral pulse signal； 3) peak value of spectral density for low frequency (LF) of amplitude and heart rate in measured peripheral pulse signal； 4) peak value of spectral density for very low frequencies (VLF) of amplitude and heart rate in measured peripheral pulse signal； 5) peak value of spectral density for ultralow frequencies (ULF) of amplitude and heart rate in measured peripheral pulse signal； 6) peak value of spectral density for high frequencies (HF) of amplitude and heart rate in measured peripheral pulse signal； 7) ratio of LF to HF (spectral ratio) of amplitude and heart rate. Device for measurement and differentiation of subject's deep sleep stage from superficial sleep stage within subject's NREM sleep stage in discretisation intervals, contains sensor for measurement in each discretisation interval of subject's peripheral pulse signal, connected with their large circulation circle； processor for analysis of measured peripheral pulse signal used for determination of said variables.
