An image forming system forms an image on body sheets and wraps, in a square shape, a stack of the body sheets having the image formed thereon with a cover to bind a book. The image forming system includes a relative-position related information input section for input of information related to a relative position between the cover and the stack of the body sheets; a storage section for storing the information related to the relative position, corresponding to a job; and a relative position control section for control of the relative position between the cover and the stack of the body sheets, based on the information related to the relative position stored in the storage section.