A method of fabricating a circular-shaped metal structure includes the steps of (a) rotating a pipe around an axis thereof, the pipe being composed of a plastic-workable metal, (b) moving a jig towards the pipe in a direction perpendicular to the axis until the jig makes contact with an outer surface of the pipe, and compressing the jig onto the pipe, (c) moving the jig in a direction in parallel with the axis with the jig being compressed onto the pipe while the pipe is kept rotated, (d) measuring a thickness of a wall of the pipe during the step (c), and (e) adjusting a pressure with which the jig is compressed onto the pipe, in accordance with the thickness measured in the step (d).