A manufacturing method for a stage tube that has a first tubular segment and a second tubular segment bordering mutually having different diameters includes: taking a metal plate that has a first segment and a second segment bordering mutually and having a first width and a second width, respectively, the first width being defined between two first paired edges, and the two second width being defined between two second paired edges; forming the first and second segments so as to define a first edge interval; rolling up the first and second segments so that the two first paired edges are jointed together and form the first tubular segment, while the second segment is formed to define a second edge interval; and rolling up the second segment so that the two second paired edges are jointed and form the second tubular segment.