A sensor relating to the present invention includes: a first electrode; a second electrode; a first attracting portion positioned between the first electrode and the second electrode and configured to receive conductive abrasion powder contained in a detection region and attracted onto the first attracting portion; a sensing unit for sensing a change in electrical resistance between the first electrode and the second electrode caused by the conductive abrasion powder; and at least one second attracting portion positioned within the detection region and configured to attract the conductive abrasion powder contained in the detection region.