A device for removing, from a processing tank, foreign material that becomes detached from a work when the work is immersed in a processing liquid held in a processing tank. The device includes a grooved part having a plurality of concave and convex shapes formed along a work-conveying direction on at least the bottom surface of the processing tank, a hopper provided in the processing tank, a processing liquid supply pipe which supplies the processing liquid circulating through the hopper to the processing tank, a plurality of branch pipes branched from the processing liquid supply pipe and arranged on ridges of the grooved part, and processing liquid discharge nozzles provided so as to face the hopper at sections of the branch pipes opposing bottom parts of the grooved part.