A vacuum pump has a casing having an inlet port and an outlet port, and a pair
of confronting pump rotors which are provided inside the casing and synchronously
rotatable for drawing in a gas from the inlet port and discharging the gas from
the outlet port. A motor for rotating the confronting pump rotors is a permanent
magnet motor having a stator and a motor rotor. The motor rotor has an iron core
and permanent magnets disposed within the iron core.
