An image forming apparatus provided with a control circuit for controlling movement of register rollers disposed on a sheet transport path extending to an image transfer section positioned around a photoconductive drum and also controlling the timing of image exposure to the photoconductive drum. The apparatus is equipped with a mechanism for detecting correlative positional error between a sheet and an image when first image formation is made in the composite image formation in which the same sheet of paper is repeatedly fed to the image transfer position.The control circuit is arranged not to stop the register rollers when a sheet is fed to the transfer position on the second image formation, and exposure timing is set corresponding to an error detected by the detecting mechanism thereby registering the images formed on the second image formation corresponding to the image formed at the first image formation irrespective of any dislocation between the sheet and the image. The registering is carried out on each sheet of paper when it is required.