The present invention relates to a synthetic quartz glass, which is a material for producing an optical member having an excellent excimer laser resistance, and a production method thereof with a good productivity. That is, the synthetic quartz glass produced by vitrifying glass fine particles obtained by flame hydrolysis of an organodisilazane compound directly on a substrate having a birefringence index of 5 nm/cm or less, a refractive index difference (&Dgr;n) of 2×10−6/cm or less, and an ArF saturated absorbance of 0.05/cm or less at a pulse energy density of 100 mJ/cm2/pulse. The production method thereof comprises the steps of introducing an organodisilazane compound represented by a general formula 1: (R1), SiNHSi(R2)3  (1) wherein R1 and R2 represent the same or a different alkyl group having 1 to 3 carbon atoms, into a flame comprising a combustion gas and a combustion-supporting gas to generate silica fine particles, and accumulating the silica fine particles on a rotating heat resistant substrate to be a molten glass.