Using atomic force microscopy we have examined the surface morphology of sequentially biaxially oriented polypropylene (BOPP) films. The surface was shown to be dominated by a nanometer-scale fiber-like network structure, the configuration of which was found to be determined by the relationship between the draw ratios used in the bi-directional stretching processes [machine draw (MD) and transverse draw (TD)]. For the film fabricated with MD and TD ratios of 5.2:1 and 9:1, respectively, preferential orientation of fine fibers to the TD direction and larger veins to the MD direction were observed. When MD and TD ratios became similar, no predominant TD direction fiber alignment and no larger veins were observed. We have shown that the residual effects of the first stretching of the film surface can provide information on the way in which morphological development of the BOPP occurs.