An abnormality detection device for a rolling bearing includes a filter that allows passage of lubricating oil, while preventing passage of metal pieces, from the bearing space between the outer ring and the inner ring of the rolling bearing to the exterior of the bearing space. The device further includes an electrical circuit including a pair of permanent magnets mounted, as a pair of electrodes, to the filter so as to be spaced apart from each other, and electrical lines extending from the respective electrodes to a power source. A state detector detects a change in electrical output from the electrical circuit when metal pieces adhere between the pair of permanent magnets, thereby detecting the state of the metal pieces contained in the lubricating oil.