PURPOSE: To improve axial load resistance, etc. by reducing diametrally the aperture end side of a container into a step shape then subjecting further the same to spinning.

CONSTITUTION: The aperture side end of a can is double-necked by plural times of pressing. The lower pat of the can is driven and rotated by a gripper 24 and the upper part is disposed with flanging rolls 26 and a pressing roll 38. The aperture end extends toward the outside in the diametral direction and is pressed by the collar of the rolls 26, by which a flange 18 is formed when the can 20 is rotate and a flanging device 28 is fed to the can 20. The aperture end of the can 20 is spinned when the roll 38 is moved in the direction A while said roll is pressed to the outside periphery of said end. The double-neck step part is thus eliminated and the diameter at the aperture end is reduced. The stress concentration in the step part is prevented by such method, by which the axial load resistance is improved and the weight of a cap is reduced as well.