Abstract: Disclosed herein is an optical biosensor. The optical biosensor includes: a substrate; a photo-sensor disposed on the substrate and generating an electrical signal upon irradiation with light; and a bio-sample layer disposed on the photo-sensor and containing a target substance to be assayed and an induction material emitting light through fluorescence, extinction or luminescence upon irradiation with light, wherein the photo-sensor is irradiated with light emitted from the induction material through fluorescence, extinction or luminescence. The optical sensor detects a spectrum of a bio-sample changed by light through the photo-sensor upon irradiation with light and converts the changed spectrum into an electrical signal, thereby enabling assay of the bio-sample without using a separate detector.