To clarify the micellar structure of the AB(3)-type polyethylene (A)-poly(ethylene glycol) (B) block copolymer, small-angle X-ray scattering and light scattering coupled with field flow fractionation were carried out. The micelle did not take the spherical form that has been observed for most polymeric micelles. The best model to fit the SAXS data was a cubic core model, presumably, relating to that the core consists of the crystallite of PE.