A sheet finishing apparatus includes: a puncher which moves between a penetrate position and a standby position; a detection unit which detects a lateral edge of a sheet; a standby tray which supports the sheet passed through the puncher, by a pair of tray members; a lateral alignment unit which holds and aligns the sheet falling off the standby tray, by a pair of alignment boards; a moving mechanism which moves the position of the standby tray or the alignment boards in a direction orthogonal to the carrying direction of the sheet; and a control unit which measures a quantity of misalignment of the sheet by using a result of detection of the lateral edge from the detection unit and controls the moving mechanism in accordance with the quantity of misalignment.