The invention relates to an automatic weighing and packaging machine. When small bags are used for packaging tea leaves at present, manual operation serves as a main part, efficiency is low, and the production cost is large. The automatic weighing and packaging machine comprises a raw material disc, a conveying belt, a quantitative allocating device, a packaging box, a packaging box bag dividing mechanism and a base of the packaging box bag dividing mechanism. The raw material disc is a vibration material disc. The conveying belt is spirally connected to the raw material disc. The front end of the conveying belt is connected with the quantitative allocating device. The quantitative allocating device comprises a tank, an overturn door and an allocating drive device. The quantitative size of the tank is set and changed through front-back adjustment of the front end portion of the conveying belt. A box body of the packaging box is in a cylindrical shape, a plurality of same independent containing cavities which do not communicate are evenly formed around the center in the box body, and the packaging box is detachably connected to the packaging box bag dividing mechanism. The packaging box bag dividing mechanism comprises a dividing disc synchronously rotating with the packaging box, and the dividing disc is provided with a dividing fork. The technical scheme is practical and convenient to implement, automatic quantitative allocating and packaging can be achieved, and efficiency is improved.