An image forming apparatus includes a first drum; first code forming means for forming a first electrostatic image code outside a developing zone for a toner image; a second drum; second code forming means for forming a second electrostatic image code outside the developing zone for the toner image; a transfer belt provided with an electrostatic image recording track capable of holding the first electrostatic image code transferred from the first drum to the second drum; transferring means for applying a voltage to a side of the transfer belt which is opposite a side contactable to the first drum to transfer the first electrostatic image code onto the electrostatic image recording track; detecting means including an electroconductive member provided which is parallel with the electrostatic image code and which is spaced from a surface of the electrostatic image code of the electrostatic image recording track to be detected with a predetermined gap, and a detecting portion for detecting an induced current generated in the electroconductive member with relative movement relative to the lines of the electrostatic image code, the detecting means detecting the first electrostatic image code of the electrostatic image recording track and the second electrostatic image code of the second drum at a position of the second drum; and control means for controlling image formation on the first drum or the second drum on the basis of a detection result of the detecting means such that the toner image on the second drum is transferred onto a recording material on the transfer belt and overlaid on the toner image transferred onto the recording material from the first drum.