We investigated the electrochemical property of Ta2O5 thin film for all-solid-state switchable mirror glass. The film was deposited by reactive dc magnetron sputtering in a mixture gas of argon and oxygen. The current density of the film covered WO3/ITO/glass was decreased with decreasing argon/oxygen ratio and working pressure measured by cyclic voltammetry. The film deposited at argon/oxygen ratio of 4.7 and working pressure of 1.0 Pa had better electrochemical property than that of other deposition condition. Its estimated proton conductivity was 2.1 x 10(-9) S/cm by conventional ac impedance method. However, the device using the film showed poor optical switching property. The transmittance change of the device at a wavelength of 670 nm was only 16% by applying voltage. On the other hand. the device using the film deposited at working pressure of 0.7 Pa was able to switch its optical switching property from reflective of 0.1% to transparent states of 44% within 15 s. These results indicate that the suitable deposition condition of the Ta2O5 thin film existed to be used for all-solid-state switchable mirror glass. (C) 2009 Elsevier B.V. All rights reserved.