An apparatus for estimating bio-information includes an optical sensor including a light source configured to emit light of multiple wavelengths onto an object, and including a plurality of detectors configured to detect light of each wavelength which is scattered or reflected from the object. The apparatus includes a processor configured to obtain spectra based on light of each wavelength which is detected by each detector, determine valid spectra of the obtained spectra, and estimate a bio-information value based on the valid spectra.