A spiral slot stacker (1) has a stacker wheel (4) for accommodating sheet material (6, 7, 8), a stripper (2) for stripping off the accommodated sheet material (6, 7, 8) and a stack deposit (9) for stacking the stripped-off sheet material (6, 7, 8). The stacker (2) is movable and in a first position strips off the sheet material (6, 7, 8) from the stacker wheel (4) in such a manner that it is intermediately stacked between the stacker wheel circumference and a guideway (3). When the stripper (2) is moved to a second position, it stacks the intermediately stacked sheet material (7) on the stack deposit (9), and subsequent sheet material (6, 7, 8) is directly stacked on the stack deposit without intermediate stacking.