This study presents a novel technique of mechanical test of nanowires (NWs). A NW standing on a substrate is deflected by means of a micro-cantilever, where interactive force like van der Waals provides adhesion enough for fixing the free end of the NW. Bent shape of the NW is observed in optical microscopy and the reactive force is measured from the cantilever deflection, detected by a laser interferometer. Luminance profile of the diffraction image provides a measure of the diameter. Inverse analysis on nonlinear mechanics successfully allows an evaluation of the Young's modulus. In addition, manipulation of the cantilever gives a fracture test based on observation of bending radius at fracture. Examples for CuO NWs showed a diameter dependence of Young's modulus and strength.