The invention relates to a rotor bearing automatic assembling machine which comprises a rack and a power distribution control box. The rack is provided with two segments of conveying troughs matched with a rotor shell, and a turning-over device is arranged between the two segments of conveying troughs; the left side of the left conveying trough is provided with a butt-joint conveyor belt matched with the left conveying trough, the other end of the butt-joint conveyor belt is connected with a feeding conveyor belt, and the tail end of the feeding conveyor belt is provided with a coil stock feeding tray connected with a coil stock motor; the left conveying trough is provided with a shell gluing device and a spooling device which are matched with the rotor shell; the right end of the right conveying trough is connected with a discharging conveying device through a discharging mechanical arm, and the right conveying trough is provided with a shaft gluing device, a bearing assembling device and a code tray assembling device which are matched with the rotor shell. The two separate conveying troughs are adopted to be matched with a feeding device to convey a rotor shell, the turning-over device is arranged at the butt-joint portion of the two conveying troughs, automated operation of a rotor bearing is achieved, and assembling efficiency is greatly improved.