Adjustment-body arrangement regions (24A) having, arranged therein, adjustment bodies (10) for adjusting the volume and flow of air streams, and non-adjustment-body arrangement regions (23A) not having the adjustment bodies (10) arranged therein are arranged in an outer layer part (2A) of a rotational drum (2), in a rotational direction of the rotational drum (2). Selective suction regions (S1) configured such that partial suction can be performed, and full suction regions (S2) configured such that full suction can be performed are arranged in that order in the rotational direction, in an outer peripheral part of a fixed drum (1). The selective suction regions (S1) are configured so as to respectively include a suction control body (6) which is disposed facing an inner peripheral surface of the rotational drum (2), and which is provided with control-body openings (61). In an inner layer part (2B) of the rotational drum (2), non-air-permeable opening-occluding members (73) are arranged which overlap and occlude the control-body openings (61) when the adjustment-body arrangement regions (24A) are positioned above the selective suction regions (S1).
