Abstract: A turbo-molecular pump has a casing, a stator fixedly mounted in the casing, and a rotor supported in the casing for rotation relatively to the stator. A turbine blade pumping assembly and a thread groove pumping assembly for discharging gas molecules are disposed between the stator and the rotor. The rotor comprises at least two components constituting the turbine blade pumping assembly and the thread groove pumping assembly. The components are separable from each other at a predetermined position, and joined to each other to form the rotor.