There is provided an elongating method of an optical fiber base material which can easily correct a distorted portion of an optical fiber base material with it being possible to elongate the optical fiber base material to reduce its diameter. According to such an elongating method, in an elongating process of elongating an optical fiber base material by heating the optical fiber base material in a heating furnace so that a diameter of the optical fiber base material is reduced, before the optical fiber base material is elongated from an end thereof, a distorted portion of the optical fiber base material is connected by being heated to be softened in the heating furnace. To do so, the optical fiber base material is attached to a hanging mechanism so as to be hung in an electric furnace, the distorted portion of the optical fiber base material is heated to be softened. The elongation is stated after a difference between the elongation axis and an end of one of the optical fiber base material and the dummy rod attached to the optical fiber base material is reduced to be 10 mm or less. Here, the difference may be detected by using a noncontact position detecting apparatus, which may be one of a laser measuring device and an image processing apparatus.