An attaching device for an annular member, for attaching the annular member to an inner peripheral surface of a tire, the attaching device comprising: a plurality of holders disposed at intervals in a circumferential direction about a predetermined axis and configured to hold an inner peripheral surface of the annular member; a moving mechanism configured to move the plurality of holders in a radial direction about the axis; a rotating mechanism configured to move the plurality of holders in the circumferential direction; and a control device, characterized in that the control device controls operation of the holders, the moving mechanism, and the rotating mechanism so as to perform the following operations (a) to (f) of: (a) holding the inner peripheral surface of the annular member by the holders; (b) moving the holders holding the annular member, outwardly in the radial direction toward a predetermined attaching position to attach a part of the annular member to the inner peripheral surface of the tire; (c) releasing the holding of the annular member by the holders; (d) moving the holders to a retraction position which is located inward of the attaching position in the radial direction, to separate the holders from the annular member; (e) moving the holders in the circumferential direction; and (f) moving the holders to the attaching position to attach another part of the annular member to the inner peripheral surface of the tire. a plurality of holders disposed at intervals in a circumferential direction about a predetermined axis and configured to hold an inner peripheral surface of the annular member; a moving mechanism configured to move the plurality of holders in a radial direction about the axis; a rotating mechanism configured to move the plurality of holders in the circumferential direction; and a control device, characterized in that the control device controls operation of the holders, the moving mechanism, and the rotating mechanism so as to perform the following operations (a) to (f) of: (a) holding the inner peripheral surface of the annular member by the holders; (b) moving the holders holding the annular member, outwardly in the radial direction toward a predetermined attaching position to attach a part of the annular member to the inner peripheral surface of the tire; (c) releasing the holding of the annular member by the holders; (d) moving the holders to a retraction position which is located inward of the attaching position in the radial direction, to separate the holders from the annular member; (e) moving the holders in the circumferential direction; and (f) moving the holders to the attaching position to attach another part of the annular member to the inner peripheral surface of the tire. (a) holding the inner peripheral surface of the annular member by the holders; (b) moving the holders holding the annular member, outwardly in the radial direction toward a predetermined attaching position to attach a part of the annular member to the inner peripheral surface of the tire; (c) releasing the holding of the annular member by the holders; (d) moving the holders to a retraction position which is located inward of the attaching position in the radial direction, to separate the holders from the annular member; (e) moving the holders in the circumferential direction; and (f) moving the holders to the attaching position to attach another part of the annular member to the inner peripheral surface of the tire.