A rotary drum (2) for a fiber-stacking device is provided with a drum body (2B), a plurality of pattern plates (6) each of which has a single fiber-stacking depression (6D), and a plurality of holding mechanisms (7), each of which holds a corresponding pattern plate (6) on the outer circumferential surface of the drum body (2BC) in a detachable manner. Each holding mechanism (7) is provided with a fixed hook which is immovably attached to one side of the drum body and which forms a fixed side holding groove (8F) with the outer circumferential surface of the drum body and with a movable hook which is attached to the other side of the drum body movably between a holding position and a release position, which forms a movable side holding groove (8M) with the outer circumferential surface of the drum body when at the holding position, and which opens the movable side holding groove when at the release position. When the movable hook (7FM) is at the holding position, the two side parts of the pattern plate (6) are accommodated inside the fixed side holding groove (8F) and the movable side holding groove (8M).
