The rotary vibrating screen used for sieving milk powder is an unbalanced weight installed up and down through a vertical vibrating motor, which converts the movement of the motor into a horizontal, vertical, and inclined three-dimensional motion, transmitted to the screen surface to drive the milk powder moving together, and the milk powder smaller than the mesh of the screen is discharged from the lower discharge port through the screen, and the milk powder larger than the mesh of the screen continues to move on the screen surface and is sieved out from the upper discharge port. In this way, the milk powder that does not meet the particle size can be screened out, ensuring the fineness of the milk powder particles, and at the same time improving the quality of the milk powder.