Electronic structures of II,III,VI, compounds are calculated by the first-principles method, for four different vacancy-ordering structures; defect chalcopyrite, defect stannite, pseudocubic and its family. It is shown that the valence-band top is made of dangling bonds of anion atoms around vacancies and its energy position hardly depends on the vacancy ordering. On the other hand, since the lowest conduction band is made the anti-bonding states of cation atoms and the cation-site vacancy acts as a potential barrier for electrons, the band-gap energy remarkably depends on the vacancy ordering.