An image fixing device having at least a pair of rotatable members for fixing a toner image on an image supporting material. In order to provide a simple structure in which the image supporting material can be readily and positively removed during jamming or the like, the apparatus includes a discharge device selectively shiftable between a normal position and a temporal retracted position, a first power transmitting member for applying a driving force to one of the rotatable members, a second power transmitting member for applying a driving force from a source of power to the first power transmitting member, cooperating elements for positioning the first and second power transmitting members selectively at an operative position in which the members cooperate to transmit the driving force and at an inoperative position in which the first power transmitting member is separated from the second power transmitting member, and a manually operable member for rotating at least one of the pair of rotatable members.