A manufacturing process for filler tube includes: a workpiece arrangement step of arranging a workpiece onto an outer peripheral mold not only to axially lock a to-be-locked portion with respect to a locking portion but also so as to make the outer peripheral mold, which is set at a predetermined temperature, support a cylinder-shaped body of the workpiece on the outer peripheral face; and a flare-molding step of flare molding a flange by inserting an inner peripheral mold, which is set at a higher temperature than the predetermined temperature of the outer peripheral mold, into a to-be-molded portion on the inner peripheral side, and by relatively moving the outer peripheral mold and the inner peripheral mold in the axial direction to make a counter-welding-face forming portion and a welding-face forming portion clamp the to-be-molded portion between them in the axial direction.