A rewinding reel for rewinding a carbon ribbon or a label carrier in a label printer is provided, including a shaft, a gear, at least two sliding bases, at least two outer casing members, a resilient element, and a knob. The gear is mounted to the shaft to mate a transmission of the label printer for driving rotation of the shaft. The sliding bases are mounted to the shaft and are rotatable by the shaft. The sliding bases include movable portions that form camming projections and follower projections respectively in camming engagement with follower projections and camming faces formed on the outer casing members to radially move the outer casing members away from and toward the sliding bases for expanding and contracting the outer casing members in order to selectively loosen the carbon ribbon or the label carrier wound around the outer casing members. The knob is fixed to the movable portions and is manually depressible to move the movable portions. The resilient element provides a biasing force that sets the movable portions at a position where the outer casing members expand.