Two electrochemical oscillations, named oscillation A and B, are observed in H2O2 reduction reaction on Pt electrodes in aqueous acidic solutions. Oscillation A appears in potentials just before Hz evolution, whereas oscillation B appears in the potential region of Hz evolution. Both oscillations are caused by alternate occurrence of H2O2 reduction and suppression of the H2O2 reduction by adsorbed hydrogen (upd-H). It is found that synchronized current oscillations are induced by external potential pulses when they are positive and located in the low-current state of oscillation. This result can be explained to be due to removal of upd-H by the positive potential pulses which lead to positive shifts of the electrode potential. The relation between the duration of the low-current state and the peak current of the high-current state is investigated and the result supports our previously propose oscillation mechanism.