Vacuum pump

A vacuum pump comprising:

• a casing in which an inlet port is provided;
• a rotating body which is enclosed in the casing and is rotatably supported;
• a stator which is substantially cylindrical and is disposed on an outer periphery of the rotating body;
• and
• a thread groove which is formed in at least one of an outer peripheral surface of the rotating body and an inner peripheral surface of the stator,
• the vacuum pump exhausting gas sucked from a side of the inlet port to outside of the casing by rotating the rotating body, wherein
• the stator extending downward from an upper end portion of the stator and having a lower extremity that is a free end, and
• a cylindrical member, which is formed of a material having a linear expansion coefficient lower than a linear expansion coefficient of a material of the stator and reduces radial deformation at a time of thermal expansion of the stator, being disposed on an outer periphery of the stator and at the lower extremity of the stator.