Disclosed is an integral label-free biosensor capable of analyzing a biomolecule with high sensitivity by integrating a light source, a photodetector, an optical waveguide, and a microcantilever on a substrate, and a method of detecting a bio-antigen by using the same. The integral label-free biosensor according to the present invention may be manufactured with low cost, be easily integrated with a silicon electron device, and detect a biomolecule with high sensitivity by using a label-free method.