Elongating method and elongating apparatus for glass base material

An elongating system for elongating a glass base material by heating the same while moving the same downward within an elongating apparatus, comprising:

• the glass base material including a transparent tapered section, wherein the transparent tapered section is located at an upper end of the glass base material and has an end face to which a suspension dummy formed from a glass pole is welded,
• the elongating apparatus including a heating furnace;
• wherein
• the elongating apparatus is configured to:
• start elongating of the glass base material by heating the same, starting from a lower-end side thereof, by causing the glass base material to pass through a range of the heating furnace within the elongating apparatus in which a preset elongating process temperature or higher is maintained, and
• after the transparent tapered section enters the range, end the elongating of the glass base material once the following condition is met:
• (X/2)<Y<{(X/2)+Z},
• where X is a length of the range in an up-down direction of the elongating apparatus [mm], Y is a length of an area extending from a central position in the range in the up-down direction to the end face [mm], and Z is a length of the transparent tapered section in the up-down direction [mm].