Organic-inorganic nanocomposites have been made by hybridization of silica nanoparticles in a thermoplastic resin using a melt extrusion method. We found that uniform dispersion of nanoparticles in the resin can be attained by the treatment of nanoparticle surfaces with an organic compound and the modification of polystyrene resin prior to mixing as well as the optimization of screw design of a twin screw extruder. Since the domain size of silica nanoparticles in the resin is smaller than the wavelength of visible light, the obtained composites are transparent in visible region, which is important for industrial applications.