PURPOSE: To make it possible to compactly and economically produce a drum separator by constituting a separator drum so as to form a return shaft of a drag chain conveyor.

CONSTITUTION: The top edge of a container 20 for a contaminated cooling lubricant is provided with an inlet 3 and the side wall of the container 20 in the region at the end face of the separator drum 6 is provided with an outlet 4 for the refined cooling lubricant. The drum 6 is driven by the drag chain 24 of the drag chain conveyor 21 which is disposed rotatably in a position parallel with the bottom of the container 20 and above by a prescribed distance and is used to discharge the sludge settled on the bottom of the container 20. Further, a drive shaft 22 is disposed above the inlet 3 and the return shaft of the conveyor 21 is disposed above the bottom of the container 20. The drum 6 is constituted to form the return shaft of the conveyor 21. Consequently, the compact and cost effective production of the drum separator is made possible.