PURPOSE: To effectively prevent a decrease in picture quality by driving a torque transmission means and resetting the transmission of torque to a conveyor belt when the reception of an image output form to heat fixing rollers is detected.

CONSTITUTION: The conveying mechanism 20 is equipped with a clutch 22 which can transmit the torque from a driving motor 5 to the conveyor belt 2, a sensor 24 which detects the photosensitive paper S being passed to the heat fixing rollers 6a and 6b, and a torque control means 26 which drives the clutch 22 when the reception of the photosensitive paper S to the heat fixing rollers 6a and 6b is detected to reset the transmission of the conveyor belt 2. Therefore, even if there is a speed difference generated between the conveyor belt 2 and heat fixing rollers 6a and 6b, the image output form is effectively prevented from deflecting and the heat fixing rollers 6a and 6b are prevented from idling on the image output form. Consequently, images of high picture quality can be formed continuously without any decrease in picture quality.