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, and a first photodetector configured to receive a first light emitted from a front surface of each of the light sources, the first light being reflected or scattered from an object. The optical sensor further includes at least one second photodetector configured to receive a second light emitted from a rear surface of each of the light sources, the second light passing through the holes corresponding to the light sources.