A taper-adjustable roller includes a support shaft, support sheets arranged circumferentially around the support shaft, and a first push member. Circumferential surfaces of the support sheets at sides of the support sheets facing away from the support shaft are assembled to form a roll surface. Each support sheet has a first end and a second end in an axial direction of the support shaft. The support sheets are swingable relative to the support shaft. The first push member is disposed on the support shaft, and is configured to push the first ends of the support sheets in a substantially radial direction, to move the first ends towards the support shaft and move the second ends away from the support shaft, or to move the first ends away from the support shaft and move the second ends towards the support shaft.