The utility model relates to a Roots blower which comprises a shell, a vane wheel, an air inlet, an air outlet and an involute type buffering air groove, wherein the buffering air groove is arranged at two sides of the air inlet side in the shell and changes from small to large and from shallow to deep; the large end of the buffering air groove is arranged at the air outlet side. The Roots blower is characterized in that when the vane wheel gets close to the air outlet, as the section area of the involute type buffering air groove is gradually formed from small to large, the communicating flow rate between a pressure cavity and the air outlet changes from small to large, the pressure at the air outlet and the pressure in the cavity are gradually balanced, so as to avoid pressure fluctuation generated by the backflow impact of high-pressure air in an exhaust opening when the pressure in the cavity is suddenly reduced, thus the vibration and noise are reduced.