To provide a pile-up device for square-bottomed paper sacks capable of piling up automatically and efficiently by replacing a prescribed number of paper sacks upside down and facilitating taking-out batch for batch.

A rising/falling plate 3 is installed in the center of the bottom plate of a sack piling part 1, and a sack supporting part 4 is provided which rises within the sack piling part 4 on both sides of the rising/falling plate 3 and falls outside to complete circulation, and a sack transporting device 7 feeds a certain number of square-bottomed sacks A alternately to the first and the second sack supplying parts 5, 6 provided in front of and behind the sack piling part 1, wherein the first sack supplying part 5 supplies each square-bottomed paper sack A on the rising/falling plate 3 with the sack bottom directed backward, and the plate 3 rises after completion of the supply from the first sack supplying part 5 and falls upon handing over the sack to the sack supporting part 4, while the second sack supplying part 6 supplies sack A with the bottom directed forward onto paper sack A supported by the sack supporting part 4, and the part 4 after the end of the supply from the second sack supplying part 6, transports the sack A toward the oversurface of the sack piling part 1.