A printed unit block aligning device that cuts a large sheet with multiple prints having an imposition structure in vertical lines and horizontal lines into printed unit blocks, aligns the printed unit blocks, and transfers the printed unit blocks at a speed constant for any imposition structure to a subsequent step, the device comprising: primary cutting means that cuts a large sheet block including a stack of the large sheets into line unit blocks arranged side by side; secondary cutting means that cuts the line unit block formed by the cutting by the primary cutting means into printed unit blocks; an upper rail that is opened and closed between a supporting position and a releasing position, the supporting position being a position where the printed unit blocks are charged in each line unit block by vertical feeding and transferring means that feeds a group of the printed unit blocks vertically; a lower rail group arranged directly below the upper rail to be perpendicular to the upper rail, the lower rail group receiving each of the printed unit blocks in a group in each line unit block dropped in response to move of the upper rail to the releasing position and feeding the group of the printed unit blocks using horizontal feeding and transferring means, wherein the device further comprises supporting means that is opened and closed between a supporting position and a releasing position, the supporting position being a position where the group of the printed unit blocks in each line unit block fed horizontally and transferred from the lower rail group is received; and an alignment transfer rail that receives the group of the printed unit blocks dropped in response to move of the supporting means to the releasing position, aligns the group of the printed unit blocks in each line unit block in a vertical direction, and feeds the group of the printed unit blocks vertically at a constant speed using alignment transferring means, characterized in that electrical controlling means is provided that electrically controls timing of drop from the supporting means onto the alignment transfer rail, and while a speed of transfer of the horizontal feeding and transferring means is determined to be uniform for any imposition structure, the electrical controlling means controls timing of drop in a manner that depends on the number of layers in each vertical line in different imposition structures, wherein the horizontal feeding and transferring means are endless conveyors which are controlled by the electrical controlling means to be temporarily halted until a vacancy for subsequent bundles opens on the alignment transfer rail, the time of halt being determined in advance depending on the number of layers or by detecting a vacancy by a sensor. primary cutting means that cuts a large sheet block including a stack of the large sheets into line unit blocks arranged side by side; secondary cutting means that cuts the line unit block formed by the cutting by the primary cutting means into printed unit blocks; an upper rail that is opened and closed between a supporting position and a releasing position, the supporting position being a position where the printed unit blocks are charged in each line unit block by vertical feeding and transferring means that feeds a group of the printed unit blocks vertically; a lower rail group arranged directly below the upper rail to be perpendicular to the upper rail, the lower rail group receiving each of the printed unit blocks in a group in each line unit block dropped in response to move of the upper rail to the releasing position and feeding the group of the printed unit blocks using horizontal feeding and transferring means, wherein the device further comprises supporting means that is opened and closed between a supporting position and a releasing position, the supporting position being a position where the group of the printed unit blocks in each line unit block fed horizontally and transferred from the lower rail group is received; and an alignment transfer rail that receives the group of the printed unit blocks dropped in response to move of the supporting means to the releasing position, aligns the group of the printed unit blocks in each line unit block in a vertical direction, and feeds the group of the printed unit blocks vertically at a constant speed using alignment transferring means, characterized in that electrical controlling means is provided that electrically controls timing of drop from the supporting means onto the alignment transfer rail, and while a speed of transfer of the horizontal feeding and transferring means is determined to be uniform for any imposition structure, the electrical controlling means controls timing of drop in a manner that depends on the number of layers in each vertical line in different imposition structures, wherein the horizontal feeding and transferring means are endless conveyors which are controlled by the electrical controlling means to be temporarily halted until a vacancy for subsequent bundles opens on the alignment transfer rail, the time of halt being determined in advance depending on the number of layers or by detecting a vacancy by a sensor.