THz polarizer is the essential device for THz polarization control, but low cost and high extinction ratio THz polarizer has been still required. We demonstrate that a stacked parallel plate waveguide THz polarizer can be fabricated by using our high-resolution 3D printer (RECILS) and metallic coating by plating. The high extinction ration as much as about 10^-3 is observed in the frequency region lower than 0.5 THz. The presented method has a possibility to be a new practical THz polarizer fabrication technique.