To maintain a self-winding watch in a wound state even at a time when the watch is not used by making the watch to rotate along a circular path around the axis of rotation of a mandrel when the mandrel rotates.

After a watch 12 is put on the outer end section of a mandrel 50, the watch 12 is pressed down along the external surface of the mandrel 50 until the watch 12 firmly coils around the mandrel 50 and does not move. When the watch 50 is put on the mandrel 50, the main body of the watch 12 is separated from the axis of rotation of the mandrel 50. Therefore, when the mandrel 50 rotates, the main body of the watch 12 makes orbital motions along a circular path around the axis of rotation of the mandrel 50. The watch 12 maintains the same interval from the axis of ration of the mandrel throughout the orbital motions. When the watch 12 makes the orbital motions, the rotary pendulum of a winding device rotates by describing circular arcs of about 60°. In this case, it is preferable to position the axis of rotation of the mandrel 50 at about 30° from the horizontal plane. When 30° is selected as the angle of the axis of rotation from the horizontal plane, the rotary pendulum makes motions by describing circular arcs of 60° at every rotation.