A rotation shaft (34) is formed in a predetermined length corresponding to four spindles, and the torque of a front bottom roller (12) is transmitted to a gear (40) formed at the center by way of an intermediate gear (42). The rotation shaft (34) has at a position corresponding to each spindle a bottom nip roller (34a) around which a part of an air-permeable apron (33) is wrapped. A sucking portion (32) extends parallel to the rotation shaft (34) and is equipped with suction holes (44a and 45a) in correspondence with the spindles. Further, the sucking portion (32) is equipped with suction pipes (44 and 45) having slide guide surfaces (44b and 45b) around which a part of the air-permeable apron (33) is wrapped so as to cover the suction holes (44a and 45a). The suction holes (44a and 45a) are arranged on the upstream side and the downstream side with the nip point of a nip roller pair therebetween.