A conveyer belt includes a conveying face which is divided into at least two areas one of which has a larger coefficient of friction than the other. Alternatively, the conveying face includes an area in which a coefficient of friction thereof varies from a large value to a small value from one side to the other side along a direction transverse to the belt. A transfer device is provided for discharging sheet material on to the conveying face of the conveyer belt in the direction transverse to the belt. The conveyer belt is disposed in such a manner that the area of the conveying face on the side of the transfer device has a larger coefficient of friction than the area on the other side.