An image processing device includes: a fold unit that folds a first adjustment sheet including an adjustment pattern, over the adjustment pattern based on a predetermined reference fold position; an image reader that reads an image of the adjustment pattern with the first adjustment sheet folded by the fold unit unfolded; a position identifying unit that, based on a fold line in the image of the adjustment pattern read by the image reader, identifies a position of the fold line; and a 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. The image reader includes a scanner that scans the first adjustment sheet relatively in a direction along fold of the first adjustment sheet, and reads the image of the adjustment pattern.