An image processing device includes: a fold unit that folds an adjustment sheet, in which an adjustment pattern is formed, over the adjustment pattern based on a predetermined reference fold position; an image reader that reads an image of the adjustment pattern of the adjustment sheet with the adjustment sheet folded by the fold unit unfolded; a position identifying unit that, based on a fold line which appears in the image of the adjustment pattern read by the image reader, identifies a position of the fold line; and a fold position adjusting unit that adjusts a fold position of the fold unit based on a difference between the position of the fold line identified by the position identifying unit and the reference fold position.