PURPOSE:To prevent stains on the reverse face of a transfer paper, by providing a paper feed detector on the route of the transfer paper in a copying apparatus for transferring a toner image through a transfer belt to detect trouble in paper feed, and releasing contact between the transfer paper and the transfer belt bearing a toner image. CONSTITUTION:Transfer paper P fed with paper feed rollers 15 stops once when its head reaches paper feed detector 16a. A latent image on charge retaining drum 1 is developed and transferred onto transfer belt 7 as a toner image, and feed of paper P is restarted in accordance with the time point when the head of the toner image reaches the pressing part of heat transfer rollers 9. 10. The head of paper P passes detector 16b after a given time, and detector 16c after another given time, and then it discharged. When trouble in its conveyance happens, detectors 16b, 16c detect that the head of paper P does not pass within each preset time, and immediately drive motors for roller 4 and outside heat transfer roller 10 and release each pressing pressure.