Thermal diffusivities of zirconia samples partially or fully stabilized by MgO and $Y_2O_3$ were measured b laser-flash method up to 140$0^{circ}C$ The values of thermal diffusivity decreased as the contents of MgO and $Y_2O_3$ increased due to the phonon scattering effect of defect structure of cubic phase formed. The temperature dependence of thermal diffusivity showed that the thermal diffusivity values decreased due to phono-phonon scattering as the temperature increased. The difference in thermal diffusivity was observed on cooling after heating up to 140$0^{circ}C$ for magnesia stabi-lized zirconia samples but not for yttria stabilized zirconia samples.