PURPOSE: To prevent transfer shifting or drum damage even in case of the displacement of a transfer roll, by positioning the center point of a photosensitive drum not on the center line between a transfer and a transfer and fixation roll.

CONSTITUTION: Even when a sheet 28 inserted into between the transfer roll 24 and transfer and fixation roll 26 is thick, the roll 24 is displaced as shown by a dotted line, but the prolongation of the straight line connecting the center points of both rolls 24 and 26 together does not run the center point of the photosensitive drum so that the extent of the displacement of the roll 24 to the photosensitive drum 20 is less than that of upward displacement. Consequently, when the thick sheet is inserted, or even when the roll 24 is displaced owing to oscillation due to the driving of a main frame, the gap between the drum 20 and roll 24 does not vary greatly; transfer shifting which used to occur is prevented and even in conveyance and installation, damage to the drum 1 due to the contacting of the roll originating from a shock is eliminated.