PURPOSE: To prevent damage, even if an overload is applied to a driving-force transmission means due to jamming or the like, by providing the driving-force transmission means with a torque limitter for controlling the torque acting on transfer rollers.

CONSTITUTION: Transfer rollers 1 for insertedly transferring a sheet while being pressed by transferring rollers are turned by the rotation of a driving gear 9 via an idle gear 8 and a transfer roller gear 7. The transfer rollers 1 and the transfer roller gear 7 constitute a torque limitter A in such a way that the taper surface 1a at the end of the roller 1 engages with the inner surface of the gear 7. The rollers 1 receive a force in the right direction by an earth spring 13, and the rollers 1 and the gear 7 are abutted on a stopper 12. If a load is applied to the transfer rollers 1 due to jamming or the like, the taper surface 1a moves to the left against the spring 13 to separate engagement, so that even if the driving gear 9 is turned, the transfer rollers 1 are not turned. Thus, damage to the gear train 7, 8, 9 can be prevented.