Morphology of a well-defined polyethylene-b-poly (ethylene-co-propylene) (PE-b-EPR) on a mica surface was analyzed by atomic force microscopy (AFM). The analyses suggested that the block copolymer, in which the PE lamella is covered with the amorphous EPR segment, can exist without aggregation and possesses a tendency to assemble to one another to form a needle-like structure.