A separation device includes a first shredding unit, a first separation unit, and a first ridge. The first shredding unit shreds a processing target containing a first material and a second material. The first separation unit rotates a first tubular portion in a state in which the processing target shredded by the first shredding unit is accommodated therein, thereby separating the second material passing through first holes from the processing target. The first ridge is provided on an inner circumferential surface of the first tubular portion, and extends in a direction in which the central axis of the first tubular portion extends.