The structure of the niobium oxide on alumina surface was investigated for low loading (5 wt.-%) and high loading (19 wt.-%) samples. The TPD profile of water molecules showed the appearance of water adsorption sites other than those on alumina. The XANES and EXAFS spectra clearly showed that niobic acid-like species are formed on the surface of 19 wt.-% NbOx/Al2O3. The XANES spectra of 5 wt.-% NbOx/Al2O3 suggests that NbO4 tetrahedra with two Nb=O bonds are present and one or two water molecules are adsorbed onto the species. On 5 wt.-% NbOx/Al2O3, the presence of a mixture of the monomer NbO4 and the dimer Nb2O7 are concluded from the EXAFS analysis.