The relationship between vortical flow behavior and aerodynamic noise has been investigated by numerical analysis on six different propeller fans. Complicated flow phenomena in the fans were captured by Reynolds-averaged Navier-Stokes flow simulation and vortex structure identification based on the critical point theory. For all the fans, the tip leakage vortex starts to be formed near the blade leading edge and grows nearly in the tangential direction, thus impinging on the pressure surface near the tip of the adjacent blade. The breakdown of the tip leakage vortex occurs near the leading edge. It is found that the behavior of the tip leakage vortex plays a major role in characteristics of the fan noise.