We propose an electrical detection method for detecting the various bio-molecules effectively with microcantilevers. The piezoresistive microcantilevers were fabricated employing surface micromachining technique that has attractive advantages in terms of cost efficiency, simplicity, and ability of fabricating in array. The fluid cell system for injection of bio-molecular solution is fabricated using polydimethylsiloxane (PDMS) and a fused silica glass. The microcantilever is deflected with respect to the difference of the surface stress caused by the formation of self-assembled bio-molecules on the gold coated side of the microcantilever. We confirmed that the deflections occurred by the bio-molecule adsorption and microcantilever can be widely used to a mu-TAS and a lab-on-a-chip as a sensor for the potential detection of various biomolecules.