To improve the accuracy in connecting a rotating member in high-speed rotation.

A rotor 7 is a cylindrical member, and a flange part 18 is circumferentially formed in a state of being projected to an inner side from an inner peripheral wall face. An inner peripheral side end part of the flange part 18 is provided with an annular projecting part 19 projecting to the shaft 6 direction. The shaft 6 is a columnar member, and has a flange part 20 projecting to an outer side, on its suction port 4 side end part. An annular projecting part 21 projecting in the suction port 4 direction is formed on an outer peripheral side end part of the flange part 20 formed on the shaft 6. The annular projecting part 21 is formed by forming a recessed groove 24 having a diameter smaller than an outer diameter of the flange part 20, on the suction port 4 side end face of the shaft 6 including the flange part 20. The rotor 7 is fixed to the shaft 6 in a state the projecting part 29 is engaged with a projecting part 21 formed on the shaft 6.