We measured an Al K-edge x-ray absorption near edge structure (XANES) spectrum of Al doped NiO for anode materials of lithium ion batteries. We found that the spectrum of the Al doped NiO is similar to that of γ -Al2O3. Calculated site-specific XANES spectra strongly correspond to the coordination nature around the absorbing Al ion, indicating aggregation of cation vacancies surrounded by Al ions in the Al doped NiO. These finding could be useful to understand how Li ions migrate in the anode.