The oxidation reaction kinetics on Ti(0001) and Ni(111) surfaces were observed by real-time photoelectron spectroscopy using synchrotron radiation to investigate the oxidation state and oxide thickness. After the Ti(0001) surface was wholly covered by TiO with a thickness of 1.2 nm, the rapid growth of n-type TiO₂ proceeded through the diffusion of Ti^4＋ ions to the TiO₂ surface at 400℃. A saturation of oxygen uptake on the TiO surface indicates that the O₂ sticking coefficient on the TiO surface is negligibly small and the segregation of Ti to the TiO surface is a trigger to initiate the TiO₂ growth. On the Ni(111) surface at 350℃, a thermally stable NiO_x layer was formed preferentially and then the growth of p-type NiO was initiated. The time evolution of NiO thickness was represented by a logarithmic growth model, where the NiO growth is governed by the electron tunneling to the NiO surface.