the intermediate tray 183 at a suitable discharge position with a suitable discharge angle and can be stacked in satisfactory manner on the intermediate tray 183 because the discharge position of the carriage unit 1 can be changed by a small amount and because the angle of the carriage rollers 20 23 of the carriage unit 1 can be regulated both depending on the number of sheets or on the physical properties of the sheet furthermore the mechanical noise and the frictional noise between the guide member and the sheet in the conventional sheet transporting apparatus employing fixed discharge path are drastically reduced by the apparatus of the present invention employing the carriage units it is furthermore possible to improve the efficiency of the image forming apparatus and to improve the stacking of the sheets s by moving the carriage unit 2 in a direction opposite to the direction of sheet discharge in the course of sheet discharge onto the intermediate tray 183 in the following there will be explained with reference to fig3 to 52 a third embodiment of the present invention in which the sheet discharge position of the carriage is varied according to the sheet size referring to fig3 a shaft 21 on which plural carriage rollers 20 are fixed in rotatably supported by lateral plates 5b 5c of a frame 5 and a pair of support levers 22 are rotatably mounted at the base portions thereof on both ends of said shaft 21 extending from said lateral plates 5b 5c a shaft 26 supports plural carriage rollers.