A box-manufacturing machine comprising: a folder gluer part that applies glue to the margins of right and left ends of a cardboard sheet, folds the cardboard sheet, and bonds together the right and left ends of the folded cardboard sheet with glue to obtain a flat cardboard box; and, a counter ejector part that stops the flat cardboard boxes fed from the folder gluer part, using a front stop, in a downstream part of a box-manufacturing machine, receives and stacks the flat cardboard boxes in a stacking part in a hopper part, and ejects the stack as a batch, a counter ejector provided in the counter ejector part in a downstream part, the counter ejector comprising: the front stop; the stacking part; and a squaring device that is configured to carry out squaring on the flat cardboard boxes in the stacking part to eliminate distortions for rectifying the flat cardboard boxes into proper rectangular shapes, the squaring device comprising: a squaring plate that is configured to square the flat cardboard boxes stacked on the stacking part, in conjunction with the front stop a reciprocation driving unit that is configured to drive the squaring plate to reciprocate in directions approaching to or departing from the front stop, the box-manufacturing machine being characterized in that: the squaring plate is configured to square each of the flat cardboard boxes stacked on the stacking part in conjunction with the front stop while the stacking part retains in a stack position during a retention interval, the retention interval being set in accordance with a feed speed of the cardboard boxes and a count setting for a stack of the cardboard boxes; wherein the reciprocation driving unit is configured to be capable of varying a speed ratio of a squaring speed for reciprocating the squaring plate, to a feed speed being defined as the number of flat cardboard boxes fed from the upstream per unit time. a folder gluer part that applies glue to the margins of right and left ends of a cardboard sheet, folds the cardboard sheet, and bonds together the right and left ends of the folded cardboard sheet with glue to obtain a flat cardboard box; and, a counter ejector part that stops the flat cardboard boxes fed from the folder gluer part, using a front stop, in a downstream part of a box-manufacturing machine, receives and stacks the flat cardboard boxes in a stacking part in a hopper part, and ejects the stack as a batch, a counter ejector provided in the counter ejector part in a downstream part, the counter ejector comprising: the front stop; the stacking part; and a squaring device that is configured to carry out squaring on the flat cardboard boxes in the stacking part to eliminate distortions for rectifying the flat cardboard boxes into proper rectangular shapes, the front stop; the stacking part; and a squaring device that is configured to carry out squaring on the flat cardboard boxes in the stacking part to eliminate distortions for rectifying the flat cardboard boxes into proper rectangular shapes, the squaring device comprising: a squaring plate that is configured to square the flat cardboard boxes stacked on the stacking part, in conjunction with the front stop a reciprocation driving unit that is configured to drive the squaring plate to reciprocate in directions approaching to or departing from the front stop, a squaring plate that is configured to square the flat cardboard boxes stacked on the stacking part, in conjunction with the front stop a reciprocation driving unit that is configured to drive the squaring plate to reciprocate in directions approaching to or departing from the front stop, the box-manufacturing machine being characterized in that: the squaring plate is configured to square each of the flat cardboard boxes stacked on the stacking part in conjunction with the front stop while the stacking part retains in a stack position during a retention interval, the retention interval being set in accordance with a feed speed of the cardboard boxes and a count setting for a stack of the cardboard boxes; wherein the reciprocation driving unit is configured to be capable of varying a speed ratio of a squaring speed for reciprocating the squaring plate, to a feed speed being defined as the number of flat cardboard boxes fed from the upstream per unit time. the squaring plate is configured to square each of the flat cardboard boxes stacked on the stacking part in conjunction with the front stop while the stacking part retains in a stack position during a retention interval, the retention interval being set in accordance with a feed speed of the cardboard boxes and a count setting for a stack of the cardboard boxes; wherein the reciprocation driving unit is configured to be capable of varying a speed ratio of a squaring speed for reciprocating the squaring plate, to a feed speed being defined as the number of flat cardboard boxes fed from the upstream per unit time.