To provide an optical sensor, and an apparatus and a method for measuring absorbance using the optical sensor.SOLUTION: An optical sensor includes: light sources configured to emit light； a substrate on which the light sources are mounted, the substrate comprising holes in regions on which the light sources are mounted； a first photodetector configured to receive first light emitted from a front surface of each of the light sources and reflected or scattered from an object； and at least one second photodetector configured to receive second light being emitted from a rear surface of each of the light sources and passing through the holes corresponding to the light sources.SELECTED DRAWING: Figure 2【課題】光センサー、それを用いた吸光度測定装置及び方法を提供する。【解決手段】一態様による光センサーは、光を照射する光源と、該光源が装着され、該光源が装着される領域にホールを含む基板と、各光源の正面から照射されて、対象体から反射または散乱された第１光を受信する第１光検出器と、各光源の背面から照射されて、該光源に対応するホールを通過した第２光を受信する少なくとも１つの第２光検出器と、を含みうる。【選択図】図２
