A method for predicting a concentration of an in vivo analyte includes obtaining a plurality of in vivo spectra of the in vivo analyte, determining a learning section for a concentration predicting algorithm for the analyte based on an unchanged section, during which the concentration of the analyte is not substantially changed, and a plurality of the in vivo spectra, and predicting the concentration of the in vivo analyte by using the concentration predicting algorithm based on a learned result of the learning section and an intrinsic spectrum of the in vivo analyte.