PURPOSE: To smooth discharge treatment on narrow site by compacting a large amt. of hydrous waste soil, etc., produced by excavation by using pressurizing and vibrating means.

CONSTITUTION: This compactor is provided with a work charging chamber 30 which can be sealed in the upper part by a freely openable and closable cover 36 and a pressurizing means 40 for pressurizing the works charged into its side part. This pressurizing means 40 has a pressurizing chamber 42 which permits traveling to attach and detach to and from the work charging chamber by a first fluid pressure means 44, a back up plate 45 which is disposed at its front surface, a vibrating means 49 which vibrates the work chamber 30 in an axial direction, a push plate 31a which constitutes one side wall of the work charging chamber 30 arranged to face the back up plate 45 and a second fluid pressure means 47 which is so connected as to move the push plate 31a connected to a rod 46 inserted with the back up plate 45 forward and backward over approximately the entire length in the axial direction of the work charging chamber 3. Further, the device has a control means for pressurizing the charged works by the fluid pressure means 44, 47 while vibrating the works by the vibrating means 49.