The electrochemical reduction of N2O was studied to investigate the electrocatalysis of oxide semiconductor electrodes. ZnO, In2O3 and In3+ doped ZnO n-type semiconductor electrodes efficiently reduced N2O to N-2 in aqueous solutions. Remarkable reduction waves of N2O were observed for ZnO and In3+ doped ZnO electrodes. In contrast, such a reduction wave was not observed for In2O3 electrodes, although N2O was efficiently reduced. These behaviors of the oxide semiconductor electrodes were quite different from those of metal electrodes.