To provide a detachable mechanism for a rotatable annular grooved leveling roller around a spindle.

A spindle (1) has an air space (4) into which a pusher (9) is inserted, and the pusher (9) has tapered thrust surfaces (9a, 9b) which displace a holder member (8) from a released position to a fixed position with a spring (10) force. The holder member (8) is arrange in the opening section provided in a wall section (3) of a tubular space (4). A plunger (11) connected to the pusher (9) works to transfer the pusher (9) to the predetermined position in the teeth of the spring (10) force. As a result, the holder member (8) can be displaced from the fixed position to the released position and the roller (7) can be detached from the spindle (1) and can be mounted to the spindle (1) again.