A cardboard box dividing device for cutting and dividing, along a width direction (Db) intersecting with a transport direction (Da), a connected cardboard box laminate in which a plurality of connected cardboard box bodies continuous along the transport direction (Da) are stacked in a thickness direction (Dc), the cardboard box dividing device comprising: a lower conveyor (121, 122) on which the plurality of connected cardboard box bodies can be stacked and transported; an upstream side positioning member movable along the transport direction (Da) and the thickness direction (Dc) of the connected cardboard box body in an upstream portion of the lower conveyor (121, 122); a downstream side positioning member movable along the transport direction (Da) and the thickness direction (Dc) of the connected cardboard box body in a downstream portion of the lower conveyor (121, 122); a positioning drive device (166 to 168, 172 to 174) capable of independently moving the upstream side positioning member and the downstream side positioning member; a pressing device configured to press, from above, the plurality of connected cardboard box bodies stacked on the lower conveyor (121, 122); a cutting knife disposed along a width direction (Db) of the connected cardboard box body and configured to divide the plurality of connected cardboard box bodies stacked on the lower conveyor (121, 122) into a front part and a rear part; and a lifting/lowering device configured to move relatively the plurality of connected cardboard box bodies on the lower conveyor (121, 122) and the cutting knife along an up-down direction characterized in that the lifting/lowering device has a lifting/lowering base configured to support the lower conveyor (121, 122) and the pressing device and a lifting/lowering drive device for lifting and lowering the lifting/lowering base, and in that the positioning drive device (166 to 168, 172 to 174) is configured to operate the upstream side positioning member and the downstream side positioning member along the thickness direction (Dc) of the connected cardboard box body as the lifting/lowering base ascends and descends. a lower conveyor (121, 122) on which the plurality of connected cardboard box bodies can be stacked and transported; an upstream side positioning member movable along the transport direction (Da) and the thickness direction (Dc) of the connected cardboard box body in an upstream portion of the lower conveyor (121, 122); a downstream side positioning member movable along the transport direction (Da) and the thickness direction (Dc) of the connected cardboard box body in a downstream portion of the lower conveyor (121, 122); a positioning drive device (166 to 168, 172 to 174) capable of independently moving the upstream side positioning member and the downstream side positioning member; a pressing device configured to press, from above, the plurality of connected cardboard box bodies stacked on the lower conveyor (121, 122); a cutting knife disposed along a width direction (Db) of the connected cardboard box body and configured to divide the plurality of connected cardboard box bodies stacked on the lower conveyor (121, 122) into a front part and a rear part; and a lifting/lowering device configured to move relatively the plurality of connected cardboard box bodies on the lower conveyor (121, 122) and the cutting knife along an up-down direction characterized in that the lifting/lowering device has a lifting/lowering base configured to support the lower conveyor (121, 122) and the pressing device and a lifting/lowering drive device for lifting and lowering the lifting/lowering base, and in that the positioning drive device (166 to 168, 172 to 174) is configured to operate the upstream side positioning member and the downstream side positioning member along the thickness direction (Dc) of the connected cardboard box body as the lifting/lowering base ascends and descends.