PURPOSE: To reduce any vibration displacement of an output shaft end while suppressing a loss of bearing parts in an electric motor directly coupled type rotary machine.

CONSTITUTION: The rotor 1 of an electric motor is provided with a main shaft 2 which rotates integrally with this rotor 1 in its state of penetrating this rotor. An impeller 3 acting as a rotary load, is directly connected to one end of the main shaft 2. The both ends of the main shaft 2 are supported by respective bearings 4 and 5 of an electric motor. The outer diameter of a bearing journal part 6 on the load side is set larger than the outer diameter of a bearing journal part 7 on the antiload side. The bearing journal part 7 on the antiload side is provided with a thrust bearing 8 of a small diameter.