PURPOSE: To form every part with required strength and to obtain the fork tube of light weight by working the prescribed length of pipe material to the both tapered end shapes with the swaging work and then forming it to the taped shape of square cross-section toward the end with the press work and the hydraulic pressurized bulge forming method.

CONSTITUTION: The pipe material 1 of light alloy, etc., is cut to the prescribed length and is worked with swaging and is formed with the tapered parts 2 at both sides and is worked to the cross-section with the strength required for the fork tube. Next, the pressing work is executed so as to make the total cross-section nearly a square shape of vertically long. On this time, in order to prevent the wrinkles of every part from generating the hydraulic pressurized bulge forming is executed to make every part a plane surface and to finish the fork tube 3. The fork tube 3 manufactured in such a way is made so that the strength over the longitudinal direction is corresponding to the practical load distribution, and is efficiently formed to light weight without waste. And because there is no welding mark at the side surface, etc., the appearance is improved.