A mobile, hydraulic-powered device for compacting the contents of containers, preferably 55 gallon drums. The compactor comprises a haulable frame having a pair of wheels, a compaction housing, two hydraulic cylinders, a hydraulic pump for operating the cylinders, a motor for operating the pump, and a complete system of operational control valves. The first hydraulic cylinder is mounted on top of the compaction housing and operates to drive a compaction plate down into a container positioned within the housing. The second hydraulic cylinder is pivotally mounted to the frame and is used to move the compaction housing between an operating position on the ground behind the frame and a transporting position up over the frame. Also, the compactor minimizes excess movement and the release of container liquids during compacting operation, which can apply a force of up to 1000 psi.