PURPOSE: To produce defect-free quartz glass having excellent light transmittance and homogeneity of refractive index, by hydrolyzing metal alkoxide with alkali and acid catalysts and by drying and sintering the obtd. dry gel at a specified temp. under reduced pressure.

CONSTITUTION: The metal alkoxide such as ethyl silicate is hydrolyzed with an alkali catalyst such as NH3. The obtd. silica sol is mixed with further metal alkoxide and hydrolyzed with an acid catalyst such as hydrochloric acid. After making dry sol from the obtd. sol, the dry sol is dried at a temp. at least up to 100°C under reduced pressure. The gel after drying is sintered at least at 900W1,400°C, preferably about 1,000W1,200°C, under ≥10-2Torr vacuum. As a result, the defect-free quartz glass having excellent light transmittance in the ultraviolet range and homogeneity of refractive index is obtd.