There is provided a method that achieves the prediction of a biological rhythm with high precision while minimizing the number of times a biological specimen is collected from a subject. There is provided a method for predicting a biological rhythm of a subject on the basis of time series expression level data obtained by measuring expression levels of two clock genes in biological specimens collected from the subject three times within 24 hours, the clock genes having different phases of circadian cycles of a change in expression levels. In this method for predicting a biological rhythm, a biological rhythm can be predicted with particularly high precision by collecting a biological specimen from a subject three times within 24 hours at eight-hour intervals.
