An image forming apparatus includes an image forming device forming an image on a recording medium wound into a roll, and a roll sheet conveyance device unwinding and conveying the medium to the image forming device. The roll sheet conveyance device includes a roll sheet feed device, a torsion detector, and a control device. The roll sheet feed device includes a drive device including upstream and downstream shafts in a drive transmission direction to rotate the medium, and a feed device to feed the medium. The detection device includes a torsion coil spring provided between the upstream and downstream shafts, and a pair of an encoder and an encoder sensor detecting the torsion amount at the opposite ends of the torsion coil spring. The control device controls the torsion amount on the basis of a signal from the detection device, and applies a given back tension to the medium.