Sodium azide (NaN₃) has been investigated by high pressure Raman scattering spectrum and theory calculation. Three pressure-induced phase transitions were observed. The phase transition pressures were determined to be 0.4, 14.1, and 27.3 GPa, respectively. In the process of the phase transition, the librational vibration mode of N₃⁻ (Eg) splits to Ag and Bg and charge transfer was observed between N₃⁻. The pressure induced-phase transition route is β-NaN₃→α-NaN₃→γ-NaN₃→δ-NaN₃. This study confirms the previous XRD study.