PURPOSE: To prevent picture disorder by eliminating a radiation heat, by providing a heat insulating plate having a slit, between a separating point of a photosensitive body and a fixing start point.

CONSTITUTION: A transfer paper 2 and a photosensitive body 1 advance at the same speed, the tip of the paper 2 reaches a photosensitive body driven roller 1b, the paper 2 cannot follow a variation of the photosensitive body 1 by a variation of a curvature of the photosensitive body 1 and the rigidity of the paper 2, and in the photosensitive body driven roller 1b, the tip of the paper 2 is separated from the photosensitive body 1 and it advances linearly. The paper 2 advances, passes through a heat insulating plate 7 consisting of ceramics of zirconium oxide having 5mm thickness, having a slit 7a having 5mm width of a fixing device 6, and it is fixed. The paper 2 is fixed without contacting other member than the atmosphere immediately after it is separated from the photosensitive body 1, and it does not occur that an unfixed toner image falls into disorder.