The planar waveguides of 12Na2O·10MgO·25GeO 2·53TeO2·1Er2O3 (MgGeEr) and 12Na2O·35WO3·53TeO 2·1Er2O3 (WEr) glasses (in mol%) were prepared by Ag+-Na+ ion-exchange. The Ag +-Na+ ion-exchange was performed by immersing the glasses in 1.0AgNO3·49.5NaNO3·49.5KNO3 melt (in mol%) at 300 - 360°C for 5 - 30 hours. The waveguide of WEr glass showed higher light scattering than that of MgGeEr glass under the same ion-exchange condition, indicating that the extent of light scattering by the waveguide surface of an ion-exchanged tellurite glass is dependent on the tellurite glass system. The effective mode indices and propagation losses of the waveguides at the wavelengths of 473, 632.8, 983.1 and 1548 nm for TE and TM mode were measured by means of a prism coupler technique. As a result, it was found that the ion-exchanged layer in the waveguide was optically isotropic and that the depth of the waveguide increased with increasing ion-exchanged temperature and time. The diffusion parameters such as diffusion coefficient and activation energy were calculated on the basis of an Arrhenius temperature dependence of the diffusion coefficient of Ag+ ions in the ion-exchanged glass. The propagation losses of the MgGeEr and WEr glass waveguides ion-exchanged at 330°C for 5 hours for TE and TM modes were about 6, 4, 6 and 7 - 8 dB/cm at 473, 632.8, 983.1 and 1548 nm, respectively. The propagation losses of ion-exchanged tellurite glass waveguides were estimated for the first time to the best of our knowledge.