The present invention provides a ball transfer unit, which includes: a main body, a first rotating body, and a plurality of second rotating bodies arranged between the main body and the first rotating body. The main body has an end forming a receiving chamber and thus forming a receiving chamber sidewall. The second rotating bodies are rotatably arranged on the receiving chamber sidewall. The main body forms an air entrance passage in communication with the receiving chamber. The receiving chamber sidewall extends out to form a bearing section corresponding to the air entrance passage. The bearing section has a side surface in which air outlet ports are formed. The ball transfer unit of the present invention prevents powder dusts from falling therein, ensures smooth operation of the ball transfer unit, and extends the lifespan.