We have developed a new polymer-blending technique with a high-shear flow field without any additives. The technique realized nano-scale dispersion of immiscible polymers. The domain sizes of the dispersed polymer phase are over one order smaller than those prepared using conventional methods. Our technique is also considered to be useful for inorganic dispersants such as carbon nanotubes. As no additive is necessary, the technique is also applicable to medicines and cosmetics.