PURPOSE: To permit the exhaust ranging from the atmospheric pressure to the superhigh vacuum range by a pump by forming a spiral gooved pump part and a centrifugal type pump into a pump case body and installing the rotors of these pump parts onto a common rotary shaft.

CONSTITUTION: The captioned pump consists of a spiral-grooved pump part 3 and a centrifugal type pump part 4, and the rotor 5 of the spiral-grooved pump part 3 and the rotor 4a of the centrifugal type pump part 4 are installed onto a common rotary shaft 6. With the revolution of a motor 8, the rotors 5a and 4a revolve through the common rotary shaft 6, and the gas supplied from a suction port 9 is compressed by a spiral-grooved pump 3 equipped with a movable vane 3A, stationary vane 3B, and a spiral groove (not shown in the figure), and further compressed by the centrifugal pump 4 and discharged from a discharge port 10. Therefore, the exhaust ranging from the atmospheric pressure to the superhigh vacuum range is enabled by a pump. Further, the necessity of a rough suction pump and an auxiliary pump, etc. in the conventional method can be eliminated, and the necessity of space can be obviated, and a simple operation is permitted.