PURPOSE: To provide a rigid long member such as a door beam for a vehicle as well as the method and device for manufacturing the same.

CONSTITUTION: The rigid long member 1 for a vehicle is such that it is provided, at both ends of a tubular central body part 3, with an end attaching part 7A, 7B for attaching the member to the place in the vehicle through a part 5A, 5B whose shape gradually changes in the cross section. Its manufacturing device is structured with plural pairs of forming rolls 23-1,..., 23-n which are provided on their circumferential faces with such part 29A, 29B for forming an end attaching part as a part of a flat sheet is formed into a planar shape having ribs 9A, 9B and positioning holes 11A1, 11A2, 11B1, 11B2; such part 33 for forming a central body part as another part of the flat sheet is formed tubularly; and such part 31A, 31B for forming the changing part of the cross sectional shape as other part of the flat sheet is so formed as the cross sectional shape gradually changes.