A calibration curve creating method includes: (a) acquiring observation data of a plurality of samples of a living body, when near infrared light is emitted to the living body and an absorbance spectrum obtained from transmitted light or diffusely-reflected light thereof is set as the observation data； (b) acquiring content of a target component of each sample； (c) estimating a plurality of independent components when the observation data of each sample is separated into the plurality of independent components, and acquiring a mixing coefficient corresponding to the target component for each sample； and (d) acquiring a regression equation of a calibration curve. (c) includes acquiring an independent component matrix by performing processes of normalization, whitening, and independent component analysis of the observation data, and the normalization is performed after a process performed by project on null space.
