To provide the rotor of a magnetic bearing motor, wherein the accuracy of the dimensions in the axial direction is easy to provide, and the coupling is strong.

In the fixing method of the rotor of a magnetic bearing motor, wherein rotors 2 and 5 for radial magnetic bearings, spacers 3, a rotor 4 of the motor, an end plate and the rotor of a thrust magnetic bearing are sequentially coupled with a shaft 1 from the side of an output shaft, a hole 12 is provided at the edge of the shaft 1 on the side of the anti-output shaft, and a taper hole or is provided in the end plate 6. Furthermore, a groove 7G, wherein a boss is coupled with the shaft 1, is made to be a cup shape, and a protrusion 72, which is coupled with a tapered hole 13 of the boss, and a tapered protrusion 71, which is coupled with the tapered hole 61 at the boss, are provided at a rotor 7 of the thrust magnetic bearing. The rotor 7 of the thrust magnetic bearing is made to have pretension with a bolt 8 and fixed to the side of the anti-output shaft of the shaft 1.