Abstract: An annular member is placed on a forming profile of a convex die without fixing the annular member to the convex die. Then, the convex die is moved toward a concave die which has an axis inclining with respect to an axis of the convex die. When the convex die is moved toward the concave die, the concave die is revolved around the axis of the convex die. The concave die does not revolve about its own axis. Revolving the concave die around the axis of the convex die may be replaced by forcibly rotating the convex die about its own axis. When a compression load is imposed on the annular member, opposed ends of the annular member are formed simultaneously.