In our previous works, hetero-junction of perovskite related oxides, (La,Sr)CoO3 and (La,Sr)2CoO4, was found to show higher catalytic activity for oxygen exchange reaction than that on the single phases of the constituent oxides. Kinetics of oxygen exchange reaction and the mechanism of the reaction promotion have been studied by in-situ characterization, isotope exchange experiments, and electrochemical measurements. Oxygen incorporation kinetics is discussed in terms of surface adsorption followed by oxygen transport through surface-most layer of the electrode. The tendency of Sr segregation on a film electrode and its suppression by addition of K2NiF4 type layer on the surface may explain partly the mechanism of reaction promotion at hetero-junction on film electrode or on bulk surface. Possibility of improving porous perovskite electrode by introduction of hetero-junction will be discussed considering the bulk and surface transport paths of oxygen in the electrode layer.