Abstract: A polymer waveguide having low optical loss and no lip around a core is prepared by using a mold having a recessed shape formed by assembling at least two waveguide pattern units having predesigned channels together with two band parts such that the channels of the units are interconnected and open to the band parts, and filling the void generated by contacting the mold and a under cladding layer with a photocurable polymeric resin to form a core layer.