PURPOSE: To eliminate paper feed labor and greatly increase the efficiency of paper feed, by turning down a cardboard stack with a tumbler and then supplying cardboards to a box making machine.

CONSTITUTION: A truck 1 is moved so that the upper end of an oblique conveyor C is placed in an appropriate position to a feed conveyor 31 for the box making machine or the like. The cardboards 4 are horizontally overlapped with one another by a horizontal conveyor A and gradually conveyed forth. The cardboards 4 are then supplied one by one or in an overlapped state onto a feed conveyor 30 by the oblique conveyor C as the cardboards are overturned as to a vertically overlapped state. When the front end of the vertically overlapped cardboards 4 is detected by a photoelectric tube (a), the tumbler B is swung counterclockwise by an air cylinder 21 to put the cardboards 4 into a horizontally overlapped state on the horizontal conveyor A. When the number of the horizontally overlapped boards cardboards 4 has become small, the tumbler B is returned to the original position through a photoelectric tube (b).