An image forming apparatus includes a stacking tray, a control unit, an alignment member and a supporting mechanism. The control unit performs a rotational sorting. An alignment member includes a leading end wall coming into contact with a leading edge of a portrait sheet stack, a pair of first side walls coming into contact with both side edges of the portrait sheet stack and a leading edge of a landscape sheet stack, and a pair of second side walls coming into contact with both side edges of the landscape sheet stack and aligning the portrait sheet stack and the landscape sheet stack. The supporting mechanism supports the alignment member so as to be movable in an alignment position where the alignment member protrudes from an upper face of the stacking tray and in a retracting position where the alignment member retracts from the upper face of the stacking tray.