Abstract: A hub setting device for a hub onto which a magnetic tape is wound with which the hub can easily be attached to and removed from a rotary shaft with substantially no play between the hub and shaft when engaged. A divided ring is retained in a recess formed in a boss portion of the shaft, and the ring is urged radially outwardly by an elastic member such as a pair of elastic tubular members. An elastic retention member is fitted around the divided ring, received completely within a recess formed around the outer circumferential surface of the ring.