PURPOSE: To form bottom part without requiring a heating device in the titled method in which the end part of a tube for a cylinder is closed by a spinning work, by rotating said tube at a high speed without preheating previously.

CONSTITUTION: A metallic tube 1 is mounted to a high speed rotating device. While rotatig it at a high speed, a forming tool 3 attached to an arm member that rotates around the tube 1 is placed at the end part 2 at an angle α to the axial line of the tube. The center (a) of rotation of the arm member is aligned with the axial line while pressing by moving the tool 3 at right angles to the axial line, and rotated successively until at least it becomes right angles to the axial line. Thus, the end part is deformed, and at the same time, frictional heat is generated by contacting the end part 2 with the front face 4 of the tool. As the tool 3 is pressed at an angle to the axial line of the tube, a component of force is generated in the axial direction. This component of force increases with rotation of the tool 3 and the bottom part is pressure welded with thickness gradually increased larger from the tube side toward the top 3 of the bottom.