A simple low-invasive method for acquiring information about a biological rhythm of a bion is provided. In the method, the information on a biological rhythm of the bion is acquired based on variation with time of the activity of a biologically active agent, particularly alpha-amylase, extracted from oral mucosa epithelial cells of the bion. According to the method, an activity variation curve showing the variation of the activity of the biologically active agent with time may be utilized as a molecular timetable for estimation of the biological rhythm, whereby a deviation (lag) of the biological rhythm of the bion can be detected.
