The present invention relates to a fabrication method for a quasi-phase-matched waveguide. The method includes the steps of forming a metal etch mask on a ferroelectric single crystal substrate, etching the substrate by using the etch mask, removing the etch mask, forming conductive layers on the etched substrate, forming polarization regions by applying an electric field to the conductive layers, and flattening the substrate after removing the conductive layers. Accordingly, the present invention is advantageous in that it can be applied to various fields employing a ferroelectric substrate, such as LiNbO3, LiTaO3, Mg:LiNbO3 or Zn:LiNbO3, it can obtain more accurate and uniform periodic domain inversion devices with a high quality and can fabricate devices that are cheaper and have a better performance.