Abstract The change of the internal friction of sodium silicate and sodium borate glasses under an electric field was studied by means of a torsion pendulum technique. It was found that the internal friction increased under an electric field and that the increase was related to the numbers of vibration, the strength of the electric field, and the Na2O content. The increase in internal friction in the glasses with a high Na2O content was large because of the electrolysis of the glasses, which resulted in the removal of sodium ions. It was proposed that the internal friction increased because the removal of sodium ions was promoted by torsional oscillation under an electric field and that the deformation of the network took place around holes which were left behind by the removal of the sodium ions.