An ultracompact, wide bandwidth, polarization beam splitter (PBS) based on a Bloch supermode coupler is proposed. In such PBS, a subwavelength grating (SWG) waveguide is sandwiched between two identical strip waveguides as a selective coupling bridge. Profiting from the tailorable characteristics of the SWG waveguide, the coupling between TM supermodes can be made negligible. On the contrary, the TE supermodes can exchange their power efficiently, resulting in short coupling length. At wavelength of 1550 nm, the extinction ratio and insertion loss of the PBS can achieve 25.5 and 0.2 dB for TE mode and 32.1 and 0.1 dB for TM mode, respectively. Furthermore, it has a 10-dB bandwidth over 200 nm and offers a width deviation tolerance of ±15  nm. The proposed PBS can find applications in the areas of polarization-sensitive interconnection and signal processing.