PROBLEM TO BE SOLVED: To provide a sleep state determination device capable of accurately estimating a slight difference in a sleep depth.SOLUTION: A sleep state determination system comprises: a vibration sensor for detecting vibration and outputting it as voltage； and a control part for reading the output signal from the vibration sensor, and analyzing the output signal. The control part sets thresholds A, B satisfying A<；B, to an output value E from the vibration sensor, then calculates S obtained by counting a number of pieces of data for unit time of A≤E<；B, and H obtained by counting a number of pieces of data for unit time of B≤E, then using the calculated S and H, calculates four parameters, and outputs a determination result of a sleep state based on the four parameters.SELECTED DRAWING: Figure 3
