The structure of a high ionic conductor Rb4Cu16I7.2C12.8 at low temperature has been reinvestigated by use of angle-dispersive neutron powder diffraction. All the diffraction data have been analyzed with integrated software REMEDY consisting of RIETAN-2000 for whole-pattern fitting and M EED for calculating densities of electrons or atomic nuclei by the maximum-entropy method. The resulting nuclear-density maps have reconfirmed that Cu1-Cu2 chains are the main conduction pathways in this material, as previously suggested from the Rietveld analysis of neutron powder diffraction data.