A deviation detection method includes obtaining first and second images of first and second electrode sheets, respectively, of an electrode assembly during winding using first and second cameras. The method further includes determining whether the first and/or second camera is deviated according to a distance from a reference point in the first and/or second image to a specific position, which is a position of a same object appearing in the first image and the second image. The method also includes determining whether the electrode assembly is deviated according to a vertical distance from the reference point in the first image to a boundary of the first electrode sheet and a vertical distance from the reference point in the second image to a boundary of the second electrode sheet if the first camera and the second camera are not deviated.