The electronic structure of ZnSb2O6 is calculated by using the FLAPW method and the DV-X alpha method. The valence band with the width of ca. 10.5 eV is roughly classified into the two bands, where O 2p orbitals are dominant and hybridize with Zn 3d and Sb 5s orbitals. On the other hand, the lower conduction band is mainly constructed from Sb 5s orbitals which have large spatial extent. Therefore, ZnSb2O6 crystal is expected to have large electron mobility with doping carriers.