There is provided a biological rhythm disturbance degree calculating device, including a physiological index time series data acquiring unit which acquires time series data of a physiological index calculated from a biomedical signal of a subject, a calculation period deciding unit which decides a calculation period which is a time length corresponding to substantially a half of a cycle with which daily-life physiological index time series data calculated from the biomedical signal measured in daily life fluctuates, a calculating unit which calculates, during the calculation period, a phase shift amount between inspected physiological index time series data calculated from the biomedical signal measured during an inspection and the daily-life physiological index time series data, and a disturbance degree deciding unit which decides a disturbance degree of a biological rhythm during the inspection of the subject based on the phase shift amount.
