We designed a compact terahertz (THz) wave polarizing beam splitter based on a periodic bilayer structure, which operates over a wide THz wavelength range. Within a short length (about 1 mm), this polarizing beam splitter separates THz wave TE- and TM-polarized modes into orthogonal output waveguides. Results of simulations with the finite-element method show that 99.99% of the TE-polarized THz wave is deflected by the periodic bilayer structure (with 39.9 dB extinction ratio), whereas 99.58% of the TM-polarized THz wave propagates through the structure (with a 23.7 dB extinction ratio). Tolerance analysis reveals a large tolerance to fabrication errors.