Vacuum pump and spiral plate, spacer, and rotating cylindrical body each included vacuum pump

A vacuum pump comprising:

• a housing in which an inlet port and an outlet port are formed;
• a rotating shaft enclosed in the housing and supported rotatably;
• spiral plates disposed in a spiral form on an outer peripheral surface of the rotating shaft or of a rotating cylinder disposed on the rotating shaft, and provided with a slit having a first side and a second side;
• a stator disc provided in the slit of the spiral plates, with a predetermined space from the slit, and having a hole portion penetrating the stator disc, the stator disc having a first side and a second side;
• spacers for fixing the stator disc;
• and
• a vacuum exhaust mechanism for transferring, to the outlet port, gas sucked from the inlet port by an interaction between the spiral plates and the stator disc, wherein
• outer diameters of the spiral plates on the first side of the slit are larger than outer diameters of the spiral plates on the second side of the slit,
• the spacers on the second side of the stator disc have a smaller inner diameter than inner diameters of the spacers on the first side of the stator disc,
• at least one of the spacers fixing the stator disc has a relief formation portion so that a part of an inner diameter of at least one of the spacers on the second side of the stator disc is equal to the inner diameter of the spacers on the first side of the stator disc, and
• the relief formation portion has an inclined portion which is inclined downstream in at least a portion of a side surface thereof opposed to one of the spiral plates.