To surely correct a curl, without massively damaging a sheet, even when using the sheet thick, rigid, and weak in surface strength.

When correcting the curl, the tip of the sheet moving along a carrying passage passes through first roller pairs 13 and 14 and a correction roller 31, and in the timing before reaching second roller pairs 35 and 36, the advancing direction of the sheet tip is changed by moving the correction roller to an advance state from a retreat state, and while moving the correction roller to the advance state from the retreat state, the sheet tip is controlled so as not to be sandwiched by the second roller pairs by staying in a position between the collection roller and the second roller pairs. The carrying passage becomes larger in the carrying passage length than the retreat state in the advance state of the correction roller, and a shape of the carrying passage made by the correction roller when correcting the curl, includes a shape of bending the sheet in the inverse direction of the direction of the curl.

COPYRIGHT: (C)2010,JPO&INPIT