Patent Number: 
Section: claims

1. A method for manufacturing a cylindrical member comprising:end bending a first end portion and a second end portion of a plate material to form a first end bending portion in which a length in a first direction is equal to or longer than a preliminary length in the first end portion and a second end bending portion in which a length in the first direction is equal to or longer than the preliminary length in the second end portion wherein the plate material extends in the first direction and includes the first end portion and the second end portion which are opposed to each other in the first direction;primary grooving each of the first end bending portion and the second end bending portion to remove each of the first end bending portion and the second end bending portion by a predetermined length of the preliminary length in the first direction while leaving extra length;bending the plate material over an entire length along the first direction, in such a manner that the plate material has a ring shape;secondary grooving each of the first end bending portion and the second end bending portion of the plate material having the ring shape; andjoining the first end bending portion and the second end bending portion to manufacture the cylindrical member. 2. The method for manufacturing a cylindrical member according to claim 1, wherein a first end surface of the first end bending portion and a second end surface of the second end bending portion which are opposed each other are processed to be parallel in the secondary grooving. 3. The method for manufacturing a cylindrical member according to claim 2, wherein the first end surface and the second end surface are processed to be parallel on the basis of an inner circumference length and an outer circumference length of the plate material having the ring shape, in the secondary grooving. 4. The method for manufacturing a cylindrical member according to claim 1, wherein the joining is performed in such a manner that the first end bending portion and the second end bending portion are joined by electron beam welding.