A rotating drum (1) has a collecting/stacking recess (2) in the outer peripheral surface thereof, and includes: a drum body (3); and an air-permeable porous member (4) that forms the bottom surface (2A) of the collecting/stacking recess (2). The porous member (4) is sandwiched between: an outer shaping member (6) arranged so as to oppose the bottom surface (2A); and an inner shaping member (7) arranged between the porous member (4) and the drum body (3). Both the shaping members (6, 7) are arranged so as to overlap the porous member (4). Each shaping member (6, 7) has a recess-bottom-surface corresponding section (6A, 7A) that overlaps the bottom surface (2A) of the collecting/stacking recess (2) in a planar view thereof, and that is constituted by: a plurality of openings (65, 75) that penetrate the recess-bottom-surface corresponding section (6A, 7A) in the thickness direction; and an opening defining section (60, 70) that partitions and forms the openings (65, 75). The opening defining section (70) of the inner shaping member (7) corresponds to the opening defining section (60) of the outer shaping member (6).