Accurate measurement of the radius of a sonoluminescing gas bubble by a light scattering method was suggested. This can be achieved because of the remarkable stability of a sonoluminescing gas bubble, which has the same shape variation sequence in every oscillation cycle with only 50 ps jitter in the time between Rashes, which enables sequential measurement of the bubble radius by the light scattering method and direct imaging technique for the first time. The measured light scattering data with an appropriate proportionality index value can be well fitted to the direct observation for the bubble radius-time curve. However, the observed value of the proportionality index is different from the one predicted by the Mie scattering theory.