An extrusion device includes a container, a pump, a plurality of pipes, and an adjustment device. The container has a chamber, and a first inlet/outlet and a second inlet/outlet connected to the chamber, wherein the chamber is adapted to contain a fluid inside. The pipes are connected between the pump and the first and second inlet/outlets of the container, so as to form a fluid loop. The pump is adapted to drive the fluid to flow inside the fluid loop. The adjustment device is coupled to the container for adjusting a volume of the chamber. Further, a coating system is also provided.