To surely convey a sheet material during its reversal by providing the first and second conveying paths, which convey the sheet material when a conveying roller is rotated normally and reversely, and conveying path switching means passing the sheet material to the second conveying path when the rear end of the sheet material passes the first conveying path.

At the same time when a rear end of a sheet material 8 passes through a tip part 3a of a guide 3 before a reversal, a sensor flag 4 is released from contact with the sheet material 8 and pulled by means of a spring 5 so as to be rotated clockwise, and an end part 4b of the sensor flag 4 enters the position in which it blocks the light of a photosensor 7, and following a lapse of the predetermined time after the detection by means of the sensor 7, a reversing roller 1 is rotated reversely and conveys the sheet material 8 in the arrow (f) direction so as to feed it into an image forming unit for printing its back face. After the sheet material rear end passes through the guide 3 before a reversal, detection by means of the photosensor 7 is carried out and the reversing roller 1 is reversed, so that the sheet material 8 does not return along the original path. In this way, no jam is caused during the reversal, and conveyance can be surely carried out.