PROBLEM TO BE SOLVED: To reduce burden to a subject in comparison with the case of using a polysomnography at sleep and detect a heart beat interval with high accuracy in comparison with a conventional system.SOLUTION: An acquisition device (S) of biological information includes: respiratory waveform calculation means (C5) for calculating a first respiratory waveform (22) based on a first stride (N1) and a vibration waveform (21), and calculating a second respiratory waveform (22) based on a second stride (N2) and a vibration waveform (21) having a period different from the first stride (N1)； pulse waveform calculation means (C6) for calculating a first pulse waveform (23) obtained by subtracting the first respiratory waveform (22) from the vibration waveform (21), and calculating a second pulse waveform (23) obtained by subtracting the second respiratory waveform (22) from the vibration waveform (21)； and index calculation means (C14) for calculating a heart rate variation index based on the pulse waveform (23), in which each peak interval (RRI) is abnormal and the number of peak intervals is small, from each pulse waveform (23).SELECTED DRAWING: Figure 3
