This paper introduces micro sub-channels to manage the liquid water in cathode flow paths in order to enhance the performance of proton exchange membrane fuel cells (PEMFCs) under high current density operating conditions. By visualization experiments, the capillary force of the micro sub-channels proves its ability to spread the liquid water on the main flow path, and consequently the main flow path possesses the space required to deliver air. Also, the advantages and disadvantages of various patterns of micro sub-channels were analyzed by comparing the liquid water movements on the main flow paths and the micro sub-channels. Finally, measuring the performance of a test PEMFC with micro sub-channels, we verified the performance enhancement that occurs in PEMFCs through the use of micro sub-channels.