Exit angle and energy dependences of the charge-state distribution of backscattered He ions were investigated when 500keV He + ions were incident on SiO 2 . The energy dependence of the He + fraction was estimated by comparing the measured He + spectra with the simulated spectra of He ions in all charge states at the exit angles of 5–25° with respect to the SiO 2 surface. We found that the He + fraction is almost independent of the exit angle at energies higher than 250keV and the observed energy dependence of the He + fraction is in good agreement with that for the carbon-foil-transmission experiment. In the low energy region (<250keV), however, the He + fraction decreases as the exit angle decreases.