The invention discloses an automatic screening and classifying device for building waste. The automatic screening and classifying device comprises a device body shell, a conveying pipe, a dust collecting box, a first screening net, a second screening net, a hydraulic rod and a vibration motor. A PLC is arranged on the upper portion of the exterior of the device body shell. A crusher is arranged onthe left side of the exterior of the device body shell. A solenoid valve is arranged in the conveying pipe. An alarm is mounted on the dust collecting box. A first collecting box is arranged on the lower portion of the exterior of the device body shell and provided with a first opening door. A third flow guiding plate is arranged below a second flow guiding plate. According to the automatic screening and classifying device, by arranging the device body shell, the PLC, an air blower, the dust collecting box, the hydraulic rod and the vibration motor, the problems that automation cannot be achieved in the screening process, a lot of manpower and time are wasted, a large amount of dust is prone to being generated in the device, and due to excessive accumulation of the dust, the device is damaged to a certain extent and the environment is polluted are solved.