The effect of thermal/electrical poling on surface structure and poling-induced second-harmonic generation have been examined for 15Nb₂O₅·85TeO₂ glass. Since the poling was carried out with the 15Nb₂O₅·85TeO₂ glass sandwiched in between two commercial borosilicate glasses containing Na⁺, penetration of Na⁺ into the anode-side surface of 15Nb₂O₅·85TeO₂ glass took place, as revealed by x-ray photoelectron spectroscopy (XPS). XPS studies also suggest that Nb⁵⁺ migrates from the anode-side surface into the bulk by the poling. It is thought that the migration of Na⁺ and Nb⁵⁺ forms an internal dc electric field, leading to the second-harmonic generation.