PURPOSE: To start the fixing roller smoothly in a simple method, by constituting so that the separating means touches or leaves the roller surface, by utilizing the deformation of a bimetal depending on the roller surface temperature.

CONSTITUTION: A separating pawl 7 is made of material of which parting propertiy is inferior to that of a fixing roller 1, and a recess part 7b is formed at its tip 7a, and a bimetal 15 is fitted in this recess. When the surface temperature of the fixing roller 1 is less than a certain temperature, for example, the softening point of the toner, the bimetal 15 curves outward of the recess 7b to contact with the surface of the fixing roller 1, so that the tip 7a is spaced from the surface of the roller 1. When the surface temperature of the fixing roller 1 reaches the specified temperature, the bimetal 15 curves inward of the recess 7b, and the tip 7a touches the surface of the roller 1. Thus, preventing increase of the torque when starting due to toner fixing, the fixing roller may be started smoothly.