This study is concerned with the improvement in efficiency of axial flow fans that are being used in numerous fields including outdoor units of air conditioners. End-wall effect, which is the main cause of loss of axial turbomachinery, has been many studied in the field of axial compressor. However, the relationships between the vortex and efficiency occurring near the hub of the axial flow fan have been seldom studied. In this study, the variation of the vortical flow field and the fan efficiency according to the hub inlet length of the axial fan were compared. As a result, it was confirmed that the efficiency was improved at the specific inlet length due to the interference between the hub vortex and the blade. This part needs to be studied further for high efficiency design of the axial flow fan.