Room temperature high-resoluion synchrotron X-ray diffraction (HRSXRD) measurements were carried out on polycrystalline samples of BiMn7O12 and LaMn7O12. Rietveld refinements of HRSXRD data describe the crystal structures of both compounds in the monoclinic space group l2/m. The maximum entropy method-based pattern fitting (MPF) method inversion of HRSXRD data was utilized to obtain the spatial electron density (ED) distribution. Obtained results show clear differences in ED distributions around Mn-O bonds between isomorphic BiMn7O12 and LaMn7O12. The scheme of ED distributions in BiMn7O12 indicates the presence of orbital ordering in the MnO2 planar arrangement that appears as prominent features in very distorted MnO12 and MnO6 polyhedrons in the perovskite related structure of [BiMn3]A-site[Mn-4](B-site)O-12.