The increase in direct current of yttria-stabilized zirconia (YSZ), which is an oxygen ionic conductor, by time-varying the strain produced by elastic waves was experimentally demonstrated. A piezo actuator was located outside of a furnace, and was used to introduce elastic waves into YSZ thin films deposited on a SiO2 bar in the furnace. Moreover, the effect of the elastic waves on the behavior of the direct current when constant voltage was applied to the YSZ films was observed. As strain increased, the direct current linearly increased at the rate of 1% for the stress application of 1 MPa at approximately 630 °C. This result considered to be due to the asymmetric strain effects in YSZ. Observed strain effects suggested the possibility of a new technology that could use elastic waves to improve the performance of high-temperature electrochemical devices, such as solid oxide fuel cells and solid oxide electrolysers.