PURPOSE: To eliminate curling, wrinkling, and oblique running, and save electric power by setting the contacting pressure of a roller lower in the fixation of the 2nd surface than in the fixation of the 1st surface.

CONSTITUTION: When the 1st surface is copied during both-surface copying operation, a roller couple rotate in press contact in response to a signal for the copy start of the 1st surface, a cam 60 stops where a recessed part 64 is detected by a sensor 61, and fixing operation is carried out in said state. When the 2nd surface is copied, the roller couple and cam 60 start rotating at the same time in response to the signal for the copy start of the 2nd surface, but the cam 60 stops once a recessed part 63 at the outer circumferential part of the cam 60 is detected by the sensor 61 and the roller couple are held in a corresponding press contact state. The fixation is carried out similarly in the 2nd surface fixation with a lower nip quantity than that in the 1st surface fixation, which is utilized to lower the contacting pressure of the roller couple in the 2nd surface fixation.