PURPOSE: To prevent the lowering of airtightness by providing a thicker double seam joint at one part of a body seam than that at the other part thereof.

CONSTITUTION: A vertical distance from a double seam roll 8 and the surface of a gripping part 1 at one part of a body seam of a container to the center line thereof is made greater than that from a double seam roll 8 and the surface of a gripping part 1 at the other part of the body seam to the center line thereof at the end of the formation of a double seam joint, thereby forming a thicker double seam joint at one part of the body seam 9 than that at the other part thereof. Therefore, the double seam joints each of which has an inner sealant filling cavity 14 adequate in size to receive the sealant at one and other part of the body seam 9 can be formed. This method prevents the excessive use of the sealant at the double seam joint and the lowering of the airtightness of the container.