To reduce the cost of optical material without deterioration in image formation performances by adjusting the synthesis condition of quartz glass used in a specific ultraviolet range and making the intensity of striae in a direction except a specified direction such as an optical axis of an optical system to be incorporated into a certain refractive index difference.

A quartz glass member to be used in an optical system having ≤400 nm wavelength light of light source has striae in a direction except a specific direction. The intensity of striae is ≤2×10-6 refractive index difference. Consequently a bad influence on the image formation performances of the quartz glass is reduced and deterioration of wave front aberration in an ultraviolet optical system can be within range of a standard. By taking the increase by wavelength of influence of the intensity of striae on wave front aberration in the operation into consideration, preferably the intensity of striae is ≤2×10-6 ×operation wavelength × 632.8 (nm) by refractive index difference. Preferably the interval between the striae is ≤2 mm and OH concentration in the quartz glass is ≤50 ppm.