PURPOSE: To securely fix or relieve a lock by restricting or relieving a core tube by providing hollow rollers that roll between both deep and shallow positions of concave parts provided on the peripheral surface of a wind-up shaft, and always make contact with the internal periphery of a wind-up core tube.

CONSTITUTION: Concave parts 2 are provided in the logitudinal and peripheral directions of a wind-up shaft 1, and a hollow roller 3 is placed on the each concave part 2 in parallel with a wind-up shaft 1 rolling between both deep and shallow positions. Moreover, a floatable pilot shaft 4 that travels together with the hollow roller 3 when the roller 3 rolls is provided on the internal periphery of the hollow roller 3. And, the hollow roller 3 always makes contact with the internal periphery of a sheet wind-up core tube C fitted into the wind-up shaft 1, and moves together with the pilot shaft 4 to the shallow position of the concave part 2 base to restrict the core tube C to the shaft 1 when turning the shaft 1 in the winding or unwinding direction relatively to the core tube C, and travels in the deep direction of the concave part 2 base to relieve the restraint when turning it in the opposite direction.