The utility model provides a compacting device, which is separately provided with an input port on the upper portion of a compactor main body and a push-off port on the front portion. Through a concave portion and convex portion, the grab of a main gate which fixedly fastens the container access is swinging mounted on a pushing block which is sliding holded in the main body of the compactor. The sliding block works forward and backward. The waste in the main body of the compactor is pushed into the container. The utility model is characterized in that, a subsidiary gate is supported by a connecting pin on the upper portion of the container access, on the other hand, a liftable lifter plate is arranged on the top portion of the push-off port of the compactor. On one side which is opposite to the subsidiary gate of the lifer plate, a storage part for storing the subsidiary gate in the lifer plate is formed. The grab of the subsidiary gate is simultaneously swinging mounted and fastened through the concave portion and convex portion. At last the compacting device capable of preventing dust overflowing or falling out from the push-off port of the compactor is provided.