The present disclosure relates to an apparatus for non-invasively estimating a target component value based on a light spectrum. The apparatus for estimating the target component value may include a sensor configured to obtain a spectrum of light scattered or reflected from an object, and a processor configured to correct a first reflectance value of the spectrum based on a melanin index; obtain a second reflectance value based on correcting the first reflectance value; convert the second reflectance value into an absorbance value; estimate the target component value based on the absorbance value; and correct the target component value based on a hemoglobin index.