To provide a plate material stacking device for moving a stacked plate material to a waiting position easily and in a short time.

The plate material stacking device is provided with a conveying device 52 including a positioning member 42, which is movably provided, for positioning a conveyed plate material 54 in a stacked position in a conveyance direction, and moving the plate material 54 positioned by the positioning member 42 and stacked in the conveyance direction and letting wait from the stacked position to the waiting position. The stacked plate material 54 is conveyed to the waiting position by the conveying device 52, the positioning member 42 is moved so as to position the newly conveyed plate material 54, and the newly conveyed plate material 54 is aligned in the stacked position to stack.