Electronic states of binary tellurite glasses have been calculated by the DV-X alpha cluster method, The calculation was achieved for several model clusters with various polymerization degrees and with various second component ions, such as glass-forming ions, intermediate ions, and modifier ions. The bonding nature of each bond in the clusters of binary tellurite glasses is discussed and compared with the silicate glasses. In the TeO4 trigonal bipyramid (tbp) unit, bond order between the Te ion and the equatorial oxygen ion (O-eq) was much larger than that between the Te ion and the axial oxygen ion (O-ax). In the cluster for the binary tellurite glasses, the bond order of the clusters with the modifier ions was almost zero. The bond order with the glass-forming ions had values larger than those with the modifier ions. In the case of the intermediate ions, the bond order ranged from -0.3 to 0.1. This change of the bond order of M-O-Te-O-M with second component ions had a similar tendency to that in the binary silicate glasses.