A sorter for sorting recording sheets after image recording by an image forming apparatus is disclosed here. The sorter is provided with a plurality of bins arrayed along a main path of the recording sheet, a plurality of change over gates to guide the recording sheet from the main path to a selected bin, a conveyance mechanism to convey the recording sheet through the main path to the selected bin, a plurality of pinch rollers dispersively located near the gates and the bins to press the recording sheet onto a conveyance surface of a conveyor belt of the conveyance mechanism and a member to back up the conveyor belt from the pressure of the pinch rollers.